diff --git a/examples/test_example_functions_fail.py b/examples/test_example_functions_fail.py
index 36755d2..91287b3 100644
--- a/examples/test_example_functions_fail.py
+++ b/examples/test_example_functions_fail.py
@@ -18,6 +18,10 @@ def test_is():
     check.is_(x, y)
 
 
+def test_is_nan():
+    check.is_nan(42)
+
+
 def test_is_not():
     x = ["foo"]
     y = x
diff --git a/examples/test_example_functions_pass.py b/examples/test_example_functions_pass.py
index e216ebe..ec93468 100644
--- a/examples/test_example_functions_pass.py
+++ b/examples/test_example_functions_pass.py
@@ -2,7 +2,7 @@
 Passing versions of all of the check helper functions.
 """
 from pytest_check import check
-
+import math
 
 def test_equal():
     check.equal(1, 1)
@@ -17,6 +17,8 @@ def test_is():
     y = x
     check.is_(x, y)
 
+def test_is_nan():
+    check.is_nan(math.nan)
 
 def test_is_not():
     x = ["foo"]
diff --git a/src/pytest_check/check_functions.py b/src/pytest_check/check_functions.py
index c601a31..9e23c61 100644
--- a/src/pytest_check/check_functions.py
+++ b/src/pytest_check/check_functions.py
@@ -1,7 +1,7 @@
 import functools
 
 import pytest
-
+import math
 from .check_log import log_failure
 
 __all__ = [
@@ -15,6 +15,7 @@
     "is_none",
     "is_not_none",
     "is_in",
+    "is_nan",
     "is_not_in",
     "is_instance",
     "is_not_instance",
@@ -75,6 +76,14 @@ def is_(a, b, msg=""):
         log_failure(f"check {a} is {b}", msg)
         return False
 
+def is_nan(a, msg=""):
+    __tracebackhide__ = True
+    if math.isnan(a):
+        return True
+    else:
+        log_failure(f"check {a} is NaN", msg)
+        return False
+
 
 def is_not(a, b, msg=""):
     __tracebackhide__ = True
diff --git a/tests/test_functions.py b/tests/test_functions.py
index 8f220b1..48f9de8 100644
--- a/tests/test_functions.py
+++ b/tests/test_functions.py
@@ -1,10 +1,10 @@
 def test_passing_check_functions(pytester):
     pytester.copy_example("examples/test_example_functions_pass.py")
     result = pytester.runpytest()
-    result.assert_outcomes(failed=0, passed=23)
+    result.assert_outcomes(failed=0, passed=24)
 
 
 def test_failing_check_functions(pytester):
     pytester.copy_example("examples/test_example_functions_fail.py")
     result = pytester.runpytest()
-    result.assert_outcomes(failed=23, passed=0)
+    result.assert_outcomes(failed=24, passed=0)