diff --git a/Doc/library/os.rst b/Doc/library/os.rst
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1729,6 +1729,16 @@
       Added support for Windows 6.0 (Vista) symbolic links.
 
 
+.. function:: realpath(path)
+
+   Return a string representing the canonicalized pathname of *path*.
+   See :manpage:`realpath(3)` for more information.
+
+   Availability: Unix
+
+   .. versionadded:: 3.3
+
+
 .. function:: remove(path)
 
    Remove (delete) the file *path*.  If *path* is a directory, :exc:`OSError` is
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -381,31 +381,7 @@
 def realpath(filename):
     """Return the canonical path of the specified filename, eliminating any
 symbolic links encountered in the path."""
-    if isinstance(filename, bytes):
-        sep = b'/'
-        empty = b''
-    else:
-        sep = '/'
-        empty = ''
-    if isabs(filename):
-        bits = [sep] + filename.split(sep)[1:]
-    else:
-        bits = [empty] + filename.split(sep)
-
-    for i in range(2, len(bits)+1):
-        component = join(*bits[0:i])
-        # Resolve symbolic links.
-        if islink(component):
-            resolved = _resolve_link(component)
-            if resolved is None:
-                # Infinite loop -- return original component + rest of the path
-                return abspath(join(*([component] + bits[i:])))
-            else:
-                newpath = join(*([resolved] + bits[i:]))
-                return realpath(newpath)
-
-    return abspath(filename)
-
+    return os.realpath(filename)
 
 def _resolve_link(path):
     """Internal helper function.  Takes a path and follows symlinks
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -7477,6 +7477,36 @@
 #endif
 
 
+#ifdef HAVE_REALPATH
+PyDoc_STRVAR(posix_realpath__doc__,
+"realpath(path) -> path\n\n\
+Return the canonicalized pathname of the given path.");
+
+static PyObject *
+posix_realpath(PyObject *self, PyObject *args)
+{
+    PyObject *opath, *orpath;
+    char *path, *rpath;
+
+    if (!PyArg_ParseTuple(args, "O&:realpath",
+                          PyUnicode_FSConverter, &opath))
+        return NULL;
+    path = PyBytes_AsString(opath);
+
+    Py_BEGIN_ALLOW_THREADS
+    rpath = realpath(path, NULL);
+    Py_END_ALLOW_THREADS
+    if (rpath == NULL)
+        return posix_error_with_allocated_filename(opath);
+
+    Py_DECREF(opath);
+    orpath = PyUnicode_DecodeFSDefault(rpath);
+    free(rpath);
+    return orpath;
+}
+#endif
+
+
 /* This is used for fpathconf(), pathconf(), confstr() and sysconf().
  * It maps strings representing configuration variable names to
  * integer values, allowing those functions to be called with the
@@ -9736,6 +9766,9 @@
 #ifdef HAVE_PATHCONF
     {"pathconf",        posix_pathconf, METH_VARARGS, posix_pathconf__doc__},
 #endif
+#ifdef HAVE_REALPATH
+    {"realpath",        posix_realpath, METH_VARARGS, posix_realpath__doc__},
+#endif /* HAVE_READLINK */
     {"abort",           posix_abort, METH_NOARGS, posix_abort__doc__},
 #ifdef MS_WINDOWS
     {"_getfullpathname",        posix__getfullpathname, METH_VARARGS, NULL},