diff --git a/Doc/library/cmath.rst b/Doc/library/cmath.rst
index 26518a0458fd81..9d2333c1ed03a1 100644
--- a/Doc/library/cmath.rst
+++ b/Doc/library/cmath.rst
@@ -340,6 +340,8 @@ Constants
    A floating-point "not a number" (NaN) value.  Equivalent to
    ``float('nan')``.
 
+   See also :data:`math.nan`.
+
    .. versionadded:: 3.6