diff --git a/icu4c/source/i18n/messageformat2.cpp b/icu4c/source/i18n/messageformat2.cpp
index 73f7fa45e69f..8e8675f741a3 100644
--- a/icu4c/source/i18n/messageformat2.cpp
+++ b/icu4c/source/i18n/messageformat2.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -11,8 +13,10 @@
 #include "unicode/messageformat2_data_model.h"
 #include "unicode/messageformat2_formattable.h"
 #include "unicode/messageformat2.h"
+#include "unicode/normalizer2.h"
 #include "unicode/unistr.h"
 #include "messageformat2_allocation.h"
+#include "messageformat2_checker.h"
 #include "messageformat2_evaluation.h"
 #include "messageformat2_macros.h"
 
@@ -37,7 +41,7 @@ static Formattable evalLiteral(const Literal& lit) {
         // The fallback for a variable name is itself.
         UnicodeString str(DOLLAR);
         str += var;
-        const Formattable* val = context.getGlobal(var, errorCode);
+        const Formattable* val = context.getGlobal(*this, var, errorCode);
         if (U_SUCCESS(errorCode)) {
             return (FormattedPlaceholder(*val, str));
         }
@@ -52,9 +56,9 @@ static Formattable evalLiteral(const Literal& lit) {
 }
 
 [[nodiscard]] FormattedPlaceholder MessageFormatter::formatOperand(const Environment& env,
-                                                             const Operand& rand,
-                                                             MessageContext& context,
-                                                             UErrorCode &status) const {
+                                                                   const Operand& rand,
+                                                                   MessageContext& context,
+                                                                   UErrorCode &status) const {
     if (U_FAILURE(status)) {
         return {};
     }
@@ -71,15 +75,19 @@ static Formattable evalLiteral(const Literal& lit) {
         // Eager vs. lazy evaluation is an open issue:
         // see https://github.com/unicode-org/message-format-wg/issues/299
 
+        // NFC-normalize the variable name. See
+        // https://github.com/unicode-org/message-format-wg/blob/main/spec/syntax.md#names-and-identifiers
+        const VariableName normalized = normalizeNFC(var);
+
         // Look up the variable in the environment
-        if (env.has(var)) {
+        if (env.has(normalized)) {
           // `var` is a local -- look it up
-          const Closure& rhs = env.lookup(var);
+          const Closure& rhs = env.lookup(normalized);
           // Format the expression using the environment from the closure
           return formatExpression(rhs.getEnv(), rhs.getExpr(), context, status);
         }
         // Variable wasn't found in locals -- check if it's global
-        FormattedPlaceholder result = evalArgument(var, context, status);
+        FormattedPlaceholder result = evalArgument(normalized, context, status);
         if (status == U_ILLEGAL_ARGUMENT_ERROR) {
             status = U_ZERO_ERROR;
             // Unbound variable -- set a resolution error
@@ -761,6 +769,7 @@ void MessageFormatter::formatSelectors(MessageContext& context, const Environmen
 UnicodeString MessageFormatter::formatToString(const MessageArguments& arguments, UErrorCode &status) {
     EMPTY_ON_ERROR(status);
 
+
     // Create a new environment that will store closures for all local variables
     Environment* env = Environment::create(status);
     // Create a new context with the given arguments and the `errors` structure
@@ -813,12 +822,14 @@ void MessageFormatter::check(MessageContext& context, const Environment& localEn
 
     // Check that variable is in scope
     const VariableName& var = rand.asVariable();
+    UnicodeString normalized = normalizeNFC(var);
+
     // Check local scope
-    if (localEnv.has(var)) {
+    if (localEnv.has(normalized)) {
         return;
     }
     // Check global scope
-    context.getGlobal(var, status);
+    context.getGlobal(*this, normalized, status);
     if (status == U_ILLEGAL_ARGUMENT_ERROR) {
         status = U_ZERO_ERROR;
         context.getErrors().setUnresolvedVariable(var, status);
@@ -855,7 +866,10 @@ void MessageFormatter::checkDeclarations(MessageContext& context, Environment*&
         // memoizing the value of localEnv up to this point
 
         // Add the LHS to the environment for checking the next declaration
-        env = Environment::create(decl.getVariable(), Closure(rhs, *env), env, status);
+        env = Environment::create(normalizeNFC(decl.getVariable()),
+                                  Closure(rhs, *env),
+                                  env,
+                                  status);
         CHECK_ERROR(status);
     }
 }
@@ -866,3 +880,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_allocation.h b/icu4c/source/i18n/messageformat2_allocation.h
index 7be27e222520..5b06d0851296 100644
--- a/icu4c/source/i18n/messageformat2_allocation.h
+++ b/icu4c/source/i18n/messageformat2_allocation.h
@@ -10,6 +10,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -139,6 +141,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_UTILS_H
diff --git a/icu4c/source/i18n/messageformat2_arguments.cpp b/icu4c/source/i18n/messageformat2_arguments.cpp
index ded3f4dda160..c43c600a2f40 100644
--- a/icu4c/source/i18n/messageformat2_arguments.cpp
+++ b/icu4c/source/i18n/messageformat2_arguments.cpp
@@ -3,12 +3,16 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
 
+#include "unicode/messageformat2.h"
 #include "unicode/messageformat2_arguments.h"
 #include "unicode/messageformat2_data_model_names.h"
+#include "messageformat2_evaluation.h"
 #include "uvector.h" // U_ASSERT
 
 U_NAMESPACE_BEGIN
@@ -22,11 +26,15 @@ namespace message2 {
 
     using Arguments = MessageArguments;
 
-    const Formattable* Arguments::getArgument(const VariableName& arg, UErrorCode& errorCode) const {
+    const Formattable* Arguments::getArgument(const MessageFormatter& context,
+                                              const VariableName& arg,
+                                              UErrorCode& errorCode) const {
         if (U_SUCCESS(errorCode)) {
             U_ASSERT(argsLen == 0 || arguments.isValid());
             for (int32_t i = 0; i < argsLen; i++) {
-                if (argumentNames[i] == arg) {
+                UnicodeString normalized = context.normalizeNFC(argumentNames[i]);
+                // arg already assumed to be normalized
+                if (normalized == arg) {
                     return &arguments[i];
                 }
             }
@@ -57,3 +65,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_checker.cpp b/icu4c/source/i18n/messageformat2_checker.cpp
index bdc5c383b6e8..535c876e42b6 100644
--- a/icu4c/source/i18n/messageformat2_checker.cpp
+++ b/icu4c/source/i18n/messageformat2_checker.cpp
@@ -3,12 +3,16 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
 
+#include "unicode/messageformat2.h"
 #include "messageformat2_allocation.h"
 #include "messageformat2_checker.h"
+#include "messageformat2_evaluation.h"
 #include "messageformat2_macros.h"
 #include "uvector.h" // U_ASSERT
 
@@ -104,6 +108,13 @@ TypeEnvironment::~TypeEnvironment() {}
 
 // ---------------------
 
+UnicodeString Checker::normalizeNFC(const Key& k) const {
+    if (k.isWildcard()) {
+        return UnicodeString("*");
+    }
+    return context.normalizeNFC(k.asLiteral().unquoted());
+}
+
 static bool areDefaultKeys(const Key* keys, int32_t len) {
     U_ASSERT(len > 0);
     for (int32_t i = 0; i < len; i++) {
@@ -185,7 +196,7 @@ void Checker::checkVariants(UErrorCode& status) {
                 // This variant was already checked,
                 // so we know keys1.len == len
                 for (int32_t kk = 0; kk < len; kk++) {
-                    if (!(keys[kk] == keys1[kk])) {
+                    if (!(normalizeNFC(keys[kk]) == normalizeNFC(keys1[kk]))) {
                         allEqual = false;
                         break;
                     }
@@ -312,3 +323,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_checker.h b/icu4c/source/i18n/messageformat2_checker.h
index 4bb0498efb99..429f79680991 100644
--- a/icu4c/source/i18n/messageformat2_checker.h
+++ b/icu4c/source/i18n/messageformat2_checker.h
@@ -10,6 +10,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -56,14 +58,19 @@ namespace message2 {
                                         // an explicit declaration
     }; // class TypeEnvironment
 
+    class MessageFormatter;
+
     // Checks a data model for semantic errors
     // (Errors are defined in https://github.com/unicode-org/message-format-wg/blob/main/spec/formatting.md       )
     class Checker {
     public:
         void check(UErrorCode&);
-        Checker(const MFDataModel& m, StaticErrors& e) : dataModel(m), errors(e) {}
+        Checker(const MFDataModel& d, StaticErrors& e, const MessageFormatter& mf)
+            : dataModel(d), errors(e), context(mf) {}
     private:
 
+        UnicodeString normalizeNFC(const Key&) const;
+
         void requireAnnotated(const TypeEnvironment&, const Expression&, UErrorCode&);
         void addFreeVars(TypeEnvironment& t, const Operand&, UErrorCode&);
         void addFreeVars(TypeEnvironment& t, const Operator&, UErrorCode&);
@@ -78,6 +85,9 @@ namespace message2 {
         void check(const Pattern&);
         const MFDataModel& dataModel;
         StaticErrors& errors;
+
+        // Used for NFC normalization
+        const MessageFormatter& context;
     }; // class Checker
 
 } // namespace message2
@@ -88,6 +98,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT_CHECKER_H
diff --git a/icu4c/source/i18n/messageformat2_data_model.cpp b/icu4c/source/i18n/messageformat2_data_model.cpp
index 3fe5f65b5323..255444082e21 100644
--- a/icu4c/source/i18n/messageformat2_data_model.cpp
+++ b/icu4c/source/i18n/messageformat2_data_model.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -918,3 +920,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_errors.cpp b/icu4c/source/i18n/messageformat2_errors.cpp
index 9d1d6bab81a1..5d3d938f0203 100644
--- a/icu4c/source/i18n/messageformat2_errors.cpp
+++ b/icu4c/source/i18n/messageformat2_errors.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -290,3 +292,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_errors.h b/icu4c/source/i18n/messageformat2_errors.h
index f84aa7362837..085263e88b06 100644
--- a/icu4c/source/i18n/messageformat2_errors.h
+++ b/icu4c/source/i18n/messageformat2_errors.h
@@ -15,6 +15,8 @@
  * \brief C++ API: Formats messages using the draft MessageFormat 2.0.
  */
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -151,6 +153,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_ERRORS_H
diff --git a/icu4c/source/i18n/messageformat2_evaluation.cpp b/icu4c/source/i18n/messageformat2_evaluation.cpp
index 41e4c9a8020a..3ba54c6b389c 100644
--- a/icu4c/source/i18n/messageformat2_evaluation.cpp
+++ b/icu4c/source/i18n/messageformat2_evaluation.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -190,13 +192,16 @@ PrioritizedVariant::~PrioritizedVariant() {}
         errors.checkErrors(status);
     }
 
-    const Formattable* MessageContext::getGlobal(const VariableName& v, UErrorCode& errorCode) const {
-       return arguments.getArgument(v, errorCode);
+    const Formattable* MessageContext::getGlobal(const MessageFormatter& context,
+                                                 const VariableName& v,
+                                                 UErrorCode& errorCode) const {
+       return arguments.getArgument(context, v, errorCode);
     }
 
     MessageContext::MessageContext(const MessageArguments& args,
                                    const StaticErrors& e,
                                    UErrorCode& status) : arguments(args), errors(e, status) {}
+
     MessageContext::~MessageContext() {}
 
 } // namespace message2
@@ -205,3 +210,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_evaluation.h b/icu4c/source/i18n/messageformat2_evaluation.h
index b8ae0242367d..ae8b4a08a3bd 100644
--- a/icu4c/source/i18n/messageformat2_evaluation.h
+++ b/icu4c/source/i18n/messageformat2_evaluation.h
@@ -14,6 +14,7 @@
  * \file
  * \brief C++ API: Formats messages using the draft MessageFormat 2.0.
  */
+#if !UCONFIG_NO_NORMALIZATION
 
 #if !UCONFIG_NO_FORMATTING
 
@@ -174,11 +175,15 @@ namespace message2 {
     // The context contains all the information needed to process
     // an entire message: arguments, formatter cache, and error list
 
+    class MessageFormatter;
+
     class MessageContext : public UMemory {
     public:
         MessageContext(const MessageArguments&, const StaticErrors&, UErrorCode&);
 
-        const Formattable* getGlobal(const VariableName&, UErrorCode&) const;
+        const Formattable* getGlobal(const MessageFormatter&,
+                                     const VariableName&,
+                                     UErrorCode&) const;
 
         // If any errors were set, update `status` accordingly
         void checkErrors(UErrorCode& status) const;
@@ -191,6 +196,7 @@ namespace message2 {
         const MessageArguments& arguments; // External message arguments
         // Errors accumulated during parsing/formatting
         DynamicErrors errors;
+
     }; // class MessageContext
 
 } // namespace message2
@@ -201,6 +207,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_EVALUATION_H
diff --git a/icu4c/source/i18n/messageformat2_formattable.cpp b/icu4c/source/i18n/messageformat2_formattable.cpp
index 3152ccb44fd8..4e2df49aeccf 100644
--- a/icu4c/source/i18n/messageformat2_formattable.cpp
+++ b/icu4c/source/i18n/messageformat2_formattable.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -336,3 +338,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_formatter.cpp b/icu4c/source/i18n/messageformat2_formatter.cpp
index 8d17ae49b99a..82f2191ba1a6 100644
--- a/icu4c/source/i18n/messageformat2_formatter.cpp
+++ b/icu4c/source/i18n/messageformat2_formatter.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -116,6 +118,24 @@ namespace message2 {
 
     // MessageFormatter
 
+    // Returns the NFC-normalized version of s, returning s itself
+    // if it's already normalized.
+    UnicodeString MessageFormatter::normalizeNFC(const UnicodeString& s) const {
+        UErrorCode status = U_ZERO_ERROR;
+        // Check if string is already normalized
+        UNormalizationCheckResult result = nfcNormalizer->quickCheck(s, status);
+        // If so, return it
+        if (U_SUCCESS(status) && result == UNORM_YES) {
+            return s;
+        }
+        // Otherwise, normalize it
+        UnicodeString normalized = nfcNormalizer->normalize(s, status);
+        if (U_FAILURE(status)) {
+            return {};
+        }
+        return normalized;
+    }
+
     MessageFormatter::MessageFormatter(const MessageFormatter::Builder& builder, UErrorCode &success) : locale(builder.locale), customMFFunctionRegistry(builder.customMFFunctionRegistry) {
         CHECK_ERROR(success);
 
@@ -163,6 +183,8 @@ namespace message2 {
             errors = errorsNew.orphan();
         }
 
+        nfcNormalizer = Normalizer2::getNFCInstance(success);
+
         // Note: we currently evaluate variables lazily,
         // without memoization. This call is still necessary
         // to check out-of-scope uses of local variables in
@@ -170,7 +192,7 @@ namespace message2 {
         // only be checked when arguments are known)
 
         // Check for resolution errors
-        Checker(dataModel, *errors).check(success);
+        Checker(dataModel, *errors, *this).check(success);
     }
 
     void MessageFormatter::cleanup() noexcept {
@@ -191,6 +213,7 @@ namespace message2 {
         signalErrors = other.signalErrors;
         errors = other.errors;
         other.errors = nullptr;
+        nfcNormalizer = other.nfcNormalizer;
         return *this;
     }
 
@@ -352,3 +375,5 @@ U_NAMESPACE_END
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_function_registry.cpp b/icu4c/source/i18n/messageformat2_function_registry.cpp
index 17955760ecfb..b4c33544dc92 100644
--- a/icu4c/source/i18n/messageformat2_function_registry.cpp
+++ b/icu4c/source/i18n/messageformat2_function_registry.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -1242,3 +1244,4 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_function_registry_internal.h b/icu4c/source/i18n/messageformat2_function_registry_internal.h
index 733fc5e945d5..46845976384e 100644
--- a/icu4c/source/i18n/messageformat2_function_registry_internal.h
+++ b/icu4c/source/i18n/messageformat2_function_registry_internal.h
@@ -10,6 +10,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -226,6 +228,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_FUNCTION_REGISTRY_INTERNAL_H
diff --git a/icu4c/source/i18n/messageformat2_macros.h b/icu4c/source/i18n/messageformat2_macros.h
index f06ed1a5a977..20e81377d4d5 100644
--- a/icu4c/source/i18n/messageformat2_macros.h
+++ b/icu4c/source/i18n/messageformat2_macros.h
@@ -10,6 +10,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -97,6 +99,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_MACROS_H
diff --git a/icu4c/source/i18n/messageformat2_parser.cpp b/icu4c/source/i18n/messageformat2_parser.cpp
index 22cb52266eaa..f435869cc48c 100644
--- a/icu4c/source/i18n/messageformat2_parser.cpp
+++ b/icu4c/source/i18n/messageformat2_parser.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -1926,3 +1928,4 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_parser.h b/icu4c/source/i18n/messageformat2_parser.h
index b62cbe9200b9..c0ed714ca6de 100644
--- a/icu4c/source/i18n/messageformat2_parser.h
+++ b/icu4c/source/i18n/messageformat2_parser.h
@@ -16,6 +16,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -175,6 +177,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT_PARSER_H
diff --git a/icu4c/source/i18n/messageformat2_serializer.cpp b/icu4c/source/i18n/messageformat2_serializer.cpp
index b2765f5acf43..6005717510a7 100644
--- a/icu4c/source/i18n/messageformat2_serializer.cpp
+++ b/icu4c/source/i18n/messageformat2_serializer.cpp
@@ -3,6 +3,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -285,3 +287,4 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/i18n/messageformat2_serializer.h b/icu4c/source/i18n/messageformat2_serializer.h
index 1b97b3b93008..f190b255f0d3 100644
--- a/icu4c/source/i18n/messageformat2_serializer.h
+++ b/icu4c/source/i18n/messageformat2_serializer.h
@@ -10,6 +10,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -63,6 +65,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT_SERIALIZER_H
diff --git a/icu4c/source/i18n/unicode/messageformat2.h b/icu4c/source/i18n/unicode/messageformat2.h
index c5459f042f40..2890985fd2e2 100644
--- a/icu4c/source/i18n/unicode/messageformat2.h
+++ b/icu4c/source/i18n/unicode/messageformat2.h
@@ -8,6 +8,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -20,6 +22,7 @@
 #include "unicode/messageformat2_arguments.h"
 #include "unicode/messageformat2_data_model.h"
 #include "unicode/messageformat2_function_registry.h"
+#include "unicode/normalizer2.h"
 #include "unicode/unistr.h"
 
 #ifndef U_HIDE_DEPRECATED_API
@@ -325,6 +328,8 @@ namespace message2 {
 
     private:
         friend class Builder;
+        friend class Checker;
+        friend class MessageArguments;
         friend class MessageContext;
 
         MessageFormatter(const MessageFormatter::Builder& builder, UErrorCode &status);
@@ -352,6 +357,9 @@ namespace message2 {
         void resolvePreferences(MessageContext&, UVector&, UVector&, UErrorCode&) const;
 
         // Formatting methods
+
+        // Used for normalizing variable names and keys for comparison
+        UnicodeString normalizeNFC(const UnicodeString&) const;
         [[nodiscard]] FormattedPlaceholder formatLiteral(const data_model::Literal&) const;
         void formatPattern(MessageContext&, const Environment&, const data_model::Pattern&, UErrorCode&, UnicodeString&) const;
         // Formats a call to a formatting function
@@ -445,6 +453,10 @@ namespace message2 {
         // formatting methods return best-effort output.
         // The default is false.
         bool signalErrors = false;
+
+        // Used for implementing normalizeNFC()
+        const Normalizer2* nfcNormalizer = nullptr;
+
     }; // class MessageFormatter
 
 } // namespace message2
@@ -457,6 +469,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_H
diff --git a/icu4c/source/i18n/unicode/messageformat2_arguments.h b/icu4c/source/i18n/unicode/messageformat2_arguments.h
index c43d96191f16..07c96f892bca 100644
--- a/icu4c/source/i18n/unicode/messageformat2_arguments.h
+++ b/icu4c/source/i18n/unicode/messageformat2_arguments.h
@@ -8,6 +8,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -43,7 +45,7 @@ template class U_I18N_API LocalArray<message2::Formattable>;
 
 namespace message2 {
 
-    class MessageContext;
+    class MessageFormatter;
 
     // Arguments
     // ----------
@@ -112,7 +114,9 @@ namespace message2 {
     private:
         friend class MessageContext;
 
-        const Formattable* getArgument(const data_model::VariableName&, UErrorCode&) const;
+        const Formattable* getArgument(const MessageFormatter&,
+                                       const data_model::VariableName&,
+                                       UErrorCode&) const;
 
         // Avoids using Hashtable so that code constructing a Hashtable
         // doesn't have to appear in this header file
@@ -131,6 +135,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_ARGUMENTS_H
diff --git a/icu4c/source/i18n/unicode/messageformat2_data_model.h b/icu4c/source/i18n/unicode/messageformat2_data_model.h
index 0c836af1bdfd..cacc271ee6cd 100644
--- a/icu4c/source/i18n/unicode/messageformat2_data_model.h
+++ b/icu4c/source/i18n/unicode/messageformat2_data_model.h
@@ -8,6 +8,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -2592,6 +2594,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT_DATA_MODEL_H
diff --git a/icu4c/source/i18n/unicode/messageformat2_formattable.h b/icu4c/source/i18n/unicode/messageformat2_formattable.h
index 8a779adb9ab3..53c500dac2f6 100644
--- a/icu4c/source/i18n/unicode/messageformat2_formattable.h
+++ b/icu4c/source/i18n/unicode/messageformat2_formattable.h
@@ -8,6 +8,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -1010,6 +1012,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_FORMATTABLE_H
diff --git a/icu4c/source/i18n/unicode/messageformat2_function_registry.h b/icu4c/source/i18n/unicode/messageformat2_function_registry.h
index b8429e3b83aa..37690d5e04a1 100644
--- a/icu4c/source/i18n/unicode/messageformat2_function_registry.h
+++ b/icu4c/source/i18n/unicode/messageformat2_function_registry.h
@@ -8,6 +8,8 @@
 
 #if U_SHOW_CPLUSPLUS_API
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -422,6 +424,8 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif /* U_SHOW_CPLUSPLUS_API */
 
 #endif // MESSAGEFORMAT2_FUNCTION_REGISTRY_H
diff --git a/icu4c/source/test/intltest/itformat.cpp b/icu4c/source/test/intltest/itformat.cpp
index 074cb993b118..49fa62f9f5c2 100644
--- a/icu4c/source/test/intltest/itformat.cpp
+++ b/icu4c/source/test/intltest/itformat.cpp
@@ -288,8 +288,10 @@ void IntlTestFormat::runIndexedTest( int32_t index, UBool exec, const char* &nam
             callTest(*test, par);
           }
           break;
+#if !UCONFIG_NO_NORMALIZATION
 #if !UCONFIG_NO_MF2
         TESTCLASS(60,TestMessageFormat2);
+#endif
 #endif
         default: name = ""; break; //needed to end loop
     }
diff --git a/icu4c/source/test/intltest/messageformat2test.cpp b/icu4c/source/test/intltest/messageformat2test.cpp
index 68a10191318a..cd3ae788f6c2 100644
--- a/icu4c/source/test/intltest/messageformat2test.cpp
+++ b/icu4c/source/test/intltest/messageformat2test.cpp
@@ -2,6 +2,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -400,3 +402,4 @@ TestCase::Builder::~Builder() {}
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/test/intltest/messageformat2test.h b/icu4c/source/test/intltest/messageformat2test.h
index 6ac2f1584e19..9fd5d253831d 100644
--- a/icu4c/source/test/intltest/messageformat2test.h
+++ b/icu4c/source/test/intltest/messageformat2test.h
@@ -7,6 +7,8 @@
 #include "unicode/rep.h"
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -188,4 +190,6 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif
diff --git a/icu4c/source/test/intltest/messageformat2test_custom.cpp b/icu4c/source/test/intltest/messageformat2test_custom.cpp
index b498be791ca9..90210e0ed061 100644
--- a/icu4c/source/test/intltest/messageformat2test_custom.cpp
+++ b/icu4c/source/test/intltest/messageformat2test_custom.cpp
@@ -2,6 +2,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -730,3 +732,5 @@ void TestMessageFormat2::testMessageRefFormatter(IcuTestErrorCode& errorCode) {
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/test/intltest/messageformat2test_icu.cpp b/icu4c/source/test/intltest/messageformat2test_icu.cpp
index d1dfa389ca8c..57361e3ccf44 100644
--- a/icu4c/source/test/intltest/messageformat2test_icu.cpp
+++ b/icu4c/source/test/intltest/messageformat2test_icu.cpp
@@ -2,6 +2,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -157,3 +159,5 @@ void TestMessageFormat2::messageFormat1Tests() {
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/test/intltest/messageformat2test_read_json.cpp b/icu4c/source/test/intltest/messageformat2test_read_json.cpp
index ddf93da632ce..43dbe1b3db01 100644
--- a/icu4c/source/test/intltest/messageformat2test_read_json.cpp
+++ b/icu4c/source/test/intltest/messageformat2test_read_json.cpp
@@ -2,6 +2,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -309,6 +311,9 @@ void TestMessageFormat2::jsonTestsFromFiles(IcuTestErrorCode& errorCode) {
     runTestsFromJsonFile(*this, "spec/functions/time.json", errorCode);
 
     // Other tests (non-spec)
+    // TODO: Delete this file after https://github.com/unicode-org/message-format-wg/pull/904
+    // lands and the tests here are updated from the spec repo
+    runTestsFromJsonFile(*this, "normalization.json", errorCode);
     runTestsFromJsonFile(*this, "more-functions.json", errorCode);
     runTestsFromJsonFile(*this, "valid-tests.json", errorCode);
     runTestsFromJsonFile(*this, "resolution-errors.json", errorCode);
@@ -358,3 +363,5 @@ void TestMessageFormat2::jsonTestsFromFiles(IcuTestErrorCode& errorCode) {
 #endif /* #if !UCONFIG_NO_MF2 */
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
diff --git a/icu4c/source/test/intltest/messageformat2test_utils.h b/icu4c/source/test/intltest/messageformat2test_utils.h
index c4ad251c7f48..336211d6e0a3 100644
--- a/icu4c/source/test/intltest/messageformat2test_utils.h
+++ b/icu4c/source/test/intltest/messageformat2test_utils.h
@@ -6,6 +6,8 @@
 
 #include "unicode/utypes.h"
 
+#if !UCONFIG_NO_NORMALIZATION
+
 #if !UCONFIG_NO_FORMATTING
 
 #if !UCONFIG_NO_MF2
@@ -344,4 +346,6 @@ U_NAMESPACE_END
 
 #endif /* #if !UCONFIG_NO_FORMATTING */
 
+#endif /* #if !UCONFIG_NO_NORMALIZATION */
+
 #endif
diff --git a/testdata/message2/normalization.json b/testdata/message2/normalization.json
new file mode 100644
index 000000000000..283e3dac8a82
--- /dev/null
+++ b/testdata/message2/normalization.json
@@ -0,0 +1,67 @@
+{
+  "$schema": "https://raw.githubusercontent.com/unicode-org/message-format-wg/main/test/schemas/v0/tests.schema.json",
+  "scenario": "Syntax",
+  "description": "Test cases that do not depend on any registry definitions.",
+  "defaultTestProperties": {
+    "locale": "en-US"
+  },
+  "tests": [
+    {
+      "description": "NFC: text is not normalized",
+      "src": "\u1E0A\u0323",
+      "exp": "\u1E0A\u0323"
+    },
+    {
+      "description": "NFC: variables are compared to each other as-if normalized; decl is non-normalized, use is",
+      "src": ".local $\u0044\u0323\u0307 = {foo} {{{$\u1E0c\u0307}}}",
+      "exp": "foo"
+    },
+    {
+      "description": "NFC: variables are compared to each other as-if normalized; decl is normalized, use isn't",
+      "src": ".local $\u1E0c\u0307 = {foo} {{{$\u0044\u0323\u0307}}}",
+      "exp": "foo"
+    },
+    {
+      "description": "NFC: variables are compared to each other as-if normalized; decl is normalized, use isn't",
+      "src": ".input {$\u1E0c\u0307} {{{$\u0044\u0323\u0307}}}",
+      "params": [{"name": "\u1E0c\u0307", "value": "foo"}],
+      "exp": "foo"
+    },
+    {
+      "description": "NFC: variables are compared to each other as-if normalized; decl is non-normalized, use is",
+      "src": ".input {$\u0044\u0323\u0307} {{{$\u1E0c\u0307}}}",
+      "params": [{"name": "\u0044\u0323\u0307", "value": "foo"}],
+      "exp": "foo"
+    },
+    {
+      "description": "NFC: variables are compared to each other as-if normalized; decl is non-normalized, use is; reordering",
+      "src": ".local $\u0044\u0307\u0323 = {foo} {{{$\u1E0c\u0307}}}",
+      "exp": "foo"
+    },
+    {
+      "description": "NFC: variables are compared to each other as-if normalized; decl is non-normalized, use is; special case mapping",
+      "src": ".local $\u0041\u030A\u0301 = {foo} {{{$\u01FA}}}",
+      "exp": "foo"
+    },
+    {
+      "description": "NFC: keys are normalized",
+      "src": ".local $x = {\u1E0C\u0307 :string} .match {$x} \u1E0A\u0323 {{Right}} * {{Wrong}}",
+      "exp": "Right"
+    },
+    {
+      "description": "NFC: keys are normalized (unquoted)",
+      "src": ".local $x = {\u1E0A\u0323 :string} .match {$x} \u1E0A\u0323 {{Not normalized}} \u1E0C\u0307 {{Normalized}} * {{Wrong}}",
+      "expErrors": [{"type": "duplicate-variant"}]
+    },
+    {
+      "description": "NFC: keys are normalized (quoted)",
+      "src": ".local $x = {\u1E0A\u0323 :string} .match {$x} |\u1E0A\u0323| {{Not normalized}} |\u1E0C\u0307| {{Normalized}} * {{Wrong}}",
+      "expErrors": [{"type": "duplicate-variant"}]
+    },
+    {
+      "description": "NFC: keys are normalized (mixed)",
+      "src": ".local $x = {\u1E0A\u0323 :string} .match {$x} \u1E0A\u0323 {{Not normalized}} |\u1E0C\u0307| {{Normalized}} * {{Wrong}}",
+      "expErrors": [{"type": "duplicate-variant"}]
+    }
+]
+}