diff --git a/Modules/cmathmodule.c b/Modules/cmathmodule.c
index 2af2e53..986b241 100644
--- a/Modules/cmathmodule.c
+++ b/Modules/cmathmodule.c
@@ -1024,6 +1024,19 @@
 Convert from polar coordinates to rectangular coordinates.");
 
 static PyObject *
+cmath_isfinite(PyObject *self, PyObject *args)
+{
+    Py_complex z;
+    if (!PyArg_ParseTuple(args, "D:isfinite", &z))
+        return NULL;
+    return PyBool_FromLong(Py_IS_FINITE(z.real) && Py_IS_FINITE(z.imag));
+}
+
+PyDoc_STRVAR(cmath_isfinite_doc,
+"isfinite(z) -> bool\n\
+Return True if both the real and imaginary parts of z are finite, else False.");
+
+static PyObject *
 cmath_isnan(PyObject *self, PyObject *args)
 {
     Py_complex z;
@@ -1065,6 +1078,7 @@
     {"cos",    cmath_cos,   METH_VARARGS, c_cos_doc},
     {"cosh",   cmath_cosh,  METH_VARARGS, c_cosh_doc},
     {"exp",    cmath_exp,   METH_VARARGS, c_exp_doc},
+    {"isfinite", cmath_isfinite, METH_VARARGS, cmath_isfinite_doc},
     {"isinf",  cmath_isinf, METH_VARARGS, cmath_isinf_doc},
     {"isnan",  cmath_isnan, METH_VARARGS, cmath_isnan_doc},
     {"log",    cmath_log,   METH_VARARGS, cmath_log_doc},
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 7f9372a..152788f 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -1818,6 +1818,19 @@
 Convert angle x from degrees to radians.");
 
 static PyObject *
+math_isfinite(PyObject *self, PyObject *arg)
+{
+    double x = PyFloat_AsDouble(arg);
+    if (x == -1.0 && PyErr_Occurred())
+        return NULL;
+    return PyBool_FromLong((long)Py_IS_FINITE(x));
+}
+
+PyDoc_STRVAR(math_isfinite_doc,
+"isfinite(x) -> bool\n\n\
+Check if float x is finite (not an infinity or NaN).");
+
+static PyObject *
 math_isnan(PyObject *self, PyObject *arg)
 {
     double x = PyFloat_AsDouble(arg);
@@ -1868,6 +1881,7 @@
     {"fsum",            math_fsum,      METH_O,         math_fsum_doc},
     {"gamma",           math_gamma,     METH_O,         math_gamma_doc},
     {"hypot",           math_hypot,     METH_VARARGS,   math_hypot_doc},
+    {"isfinite",        math_isfinite,  METH_O,         math_isfinite_doc},
     {"isinf",           math_isinf,     METH_O,         math_isinf_doc},
     {"isnan",           math_isnan,     METH_O,         math_isnan_doc},
     {"ldexp",           math_ldexp,     METH_VARARGS,   math_ldexp_doc},