diff --git a/kotlin-result/src/commonMain/kotlin/com/github/michaelbull/result/ThrowIfUnless.kt b/kotlin-result/src/commonMain/kotlin/com/github/michaelbull/result/ThrowIfUnless.kt
new file mode 100644
index 0000000..087e6ad
--- /dev/null
+++ b/kotlin-result/src/commonMain/kotlin/com/github/michaelbull/result/ThrowIfUnless.kt
@@ -0,0 +1,27 @@
+package com.github.michaelbull.result
+
+import kotlin.contracts.InvocationKind
+import kotlin.contracts.contract
+
+/**
+ * If the [Result] is [Err] and contains a [Throwable], throws the [error][Err.error]
+ * if the [predicate] returns true.
+ *
+ * @throws E if [predicate] returns true.
+ */
+public inline fun <V : Any?, E : Throwable> Result<V, E>.throwIf(
+    predicate: (E) -> Boolean
+): Result<V, E> {
+    contract { callsInPlace(predicate, InvocationKind.AT_MOST_ONCE)  }
+    return onFailure { e -> if (predicate(e)) throw e }
+}
+
+/**
+ * If the [Result] is [Err] and contains a [Throwable], throws the [error][Err.error]
+ * only if the [predicate] returns false.
+ *
+ * @throws E if [predicate] returns false.
+ */
+public inline fun <V : Any?, E : Throwable> Result<V, E>.throwUnless(
+    predicate: (E) -> Boolean
+): Result<V, E> = throwIf { e -> predicate(e).not() }
diff --git a/kotlin-result/src/commonTest/kotlin/com/github/michaelbull/result/ThrowTest.kt b/kotlin-result/src/commonTest/kotlin/com/github/michaelbull/result/ThrowTest.kt
new file mode 100644
index 0000000..04ac939
--- /dev/null
+++ b/kotlin-result/src/commonTest/kotlin/com/github/michaelbull/result/ThrowTest.kt
@@ -0,0 +1,64 @@
+package com.github.michaelbull.result
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+
+class ThrowTest {
+
+    class ThrowIfTest {
+        @Test
+        fun throwsIfPredicateReturnsTrue() {
+            val result: Result<Any, Throwable> = Err(RuntimeException())
+
+            assertFailsWith<RuntimeException> {
+                result.throwIf { _ -> true }
+            }
+        }
+
+        @Test
+        fun nothingThrownIfPredicateReturnsFalse() {
+            val result: Result<Any, Exception> = Err(NullPointerException())
+
+            result.throwIf { _ -> false }
+        }
+
+        @Test
+        fun doesntAlterOkValue() {
+            val result: Result<String, Throwable> = Ok("ok")
+
+            assertEquals(
+                expected = "ok",
+                actual = result.throwIf(predicate = { false }).unwrap()
+            )
+        }
+    }
+
+    class ThrowUnlessTest {
+        @Test
+        fun throwsIfPredicateReturnsFalse() {
+            val result: Result<Any, Throwable> = Err(RuntimeException())
+
+            assertFailsWith<RuntimeException> {
+                result.throwUnless { _ -> false }
+            }
+        }
+
+        @Test
+        fun nothingThrownIfPredicateReturnsTrue() {
+            val result: Result<Any, Exception> = Err(NullPointerException())
+
+            result.throwUnless { _ -> true }
+        }
+
+        @Test
+        fun doesntAlterOkValue() {
+            val result: Result<String, Throwable> = Ok("ok")
+
+            assertEquals(
+                expected = "ok",
+                actual = result.throwUnless(predicate = { false }).unwrap()
+            )
+        }
+    }
+}