diff --git a/Doc/library/os.path.rst b/Doc/library/os.path.rst
index d06d9ce8c9e3d7..517b6e6645d52a 100644
--- a/Doc/library/os.path.rst
+++ b/Doc/library/os.path.rst
@@ -205,6 +205,14 @@ the :mod:`glob` module.)
       Accepts a :term:`path-like object`.
 
 
+.. function:: fileuri(path):
+
+    Represent the given path as a ``file://`` URI.  :exc:`ValueError` is raised
+    if the path isn't absolute.
+
+   .. versionadded:: 3.11
+
+
 .. function:: getatime(path)
 
    Return the time of last access of *path*.  The return value is a floating point number giving
diff --git a/Doc/library/pathlib.rst b/Doc/library/pathlib.rst
index b6507eb4d6fa2c..9e2bd77965f111 100644
--- a/Doc/library/pathlib.rst
+++ b/Doc/library/pathlib.rst
@@ -1274,6 +1274,7 @@ Below is a table mapping various :mod:`os` functions to their corresponding
 :func:`os.path.dirname`                :data:`PurePath.parent`
 :func:`os.path.samefile`               :meth:`Path.samefile`
 :func:`os.path.splitext`               :data:`PurePath.suffix`
+:func:`os.path.fileuri`                :meth:`PurePath.as_uri`
 ====================================   ==============================
 
 .. rubric:: Footnotes
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index 527c7ae1938fbb..69daa262aceeed 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -22,6 +22,7 @@
 import stat
 import genericpath
 from genericpath import *
+from urllib.parse import quote_from_bytes as urlquote
 
 __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
@@ -29,7 +30,7 @@
            "ismount", "expanduser","expandvars","normpath","abspath",
            "curdir","pardir","sep","pathsep","defpath","altsep",
            "extsep","devnull","realpath","supports_unicode_filenames","relpath",
-           "samefile", "sameopenfile", "samestat", "commonpath"]
+           "samefile", "sameopenfile", "samestat", "commonpath", "fileuri"]
 
 def _get_bothseps(path):
     if isinstance(path, bytes):
@@ -798,6 +799,33 @@ def commonpath(paths):
         raise
 
 
+def fileuri(path):
+    """
+    Return the given path expressed as a ``file://`` URI.
+    """
+
+    # File URIs use the UTF-8 encoding on Windows.
+    path = os.fspath(path)
+    if not isinstance(path, bytes):
+        path = path.encode('utf8')
+
+    # Strip UNC prefixes
+    path = path.replace(b'\\', b'/')
+    if path.startswith(b'//?/UNC/'):
+        path = b'//' + path[8:]
+    elif path.startswith(b'//?/'):
+        path = path[4:]
+
+    if path[1:3] == b':/':
+        # It's a path on a local drive => 'file:///c:/a/b'
+        return 'file:///' + urlquote(path[:1]) + ':' + urlquote(path[2:])
+    elif path[0:2] == b'//':
+        # It's a path on a network drive => 'file://host/share/a/b'
+        return 'file:' + urlquote(path)
+    else:
+        raise ValueError("relative path can't be expressed as a file URI")
+
+
 try:
     # The genericpath.isdir implementation uses os.stat and checks the mode
     # attribute to tell whether or not the path is a directory.
diff --git a/Lib/nturl2path.py b/Lib/nturl2path.py
index 61852aff58912d..d3381806a8cd4f 100644
--- a/Lib/nturl2path.py
+++ b/Lib/nturl2path.py
@@ -3,6 +3,9 @@
 This module only exists to provide OS-specific code
 for urllib.requests, thus do not use directly.
 """
+
+import ntpath
+
 # Testing is done through test_urllib.
 
 def url2pathname(url):
@@ -49,33 +52,7 @@ def pathname2url(p):
     #   C:\foo\bar\spam.foo
     # becomes
     #   ///C:/foo/bar/spam.foo
-    import urllib.parse
-    # First, clean up some special forms. We are going to sacrifice
-    # the additional information anyway
-    if p[:4] == '\\\\?\\':
-        p = p[4:]
-        if p[:4].upper() == 'UNC\\':
-            p = '\\' + p[4:]
-        elif p[1:2] != ':':
-            raise OSError('Bad path: ' + p)
-    if not ':' in p:
-        # No drive specifier, just convert slashes and quote the name
-        if p[:2] == '\\\\':
-        # path is something like \\host\path\on\remote\host
-        # convert this to ////host/path/on/remote/host
-        # (notice doubling of slashes at the start of the path)
-            p = '\\\\' + p
-        components = p.split('\\')
-        return urllib.parse.quote('/'.join(components))
-    comp = p.split(':', maxsplit=2)
-    if len(comp) != 2 or len(comp[0]) > 1:
-        error = 'Bad path: ' + p
-        raise OSError(error)
-
-    drive = urllib.parse.quote(comp[0].upper())
-    components = comp[1].split('\\')
-    path = '///' + drive + ':'
-    for comp in components:
-        if comp:
-            path = path + '/' + urllib.parse.quote(comp)
-    return path
+    try:
+        return ntpath.fileuri(p).removeprefix('file:')
+    except ValueError:
+        raise OSError('Bad path: ' + p)
diff --git a/Lib/pathlib.py b/Lib/pathlib.py
index 8e6eb48b9767ca..92f21a6b12cabc 100644
--- a/Lib/pathlib.py
+++ b/Lib/pathlib.py
@@ -11,7 +11,6 @@
 from errno import EINVAL, ENOENT, ENOTDIR, EBADF, ELOOP
 from operator import attrgetter
 from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
-from urllib.parse import quote_from_bytes as urlquote_from_bytes
 
 
 __all__ = [
@@ -205,18 +204,6 @@ def is_reserved(self, parts):
             return False
         return parts[-1].partition('.')[0].upper() in self.reserved_names
 
-    def make_uri(self, path):
-        # Under Windows, file URIs use the UTF-8 encoding.
-        drive = path.drive
-        if len(drive) == 2 and drive[1] == ':':
-            # It's a path on a local drive => 'file:///c:/a/b'
-            rest = path.as_posix()[2:].lstrip('/')
-            return 'file:///%s/%s' % (
-                drive, urlquote_from_bytes(rest.encode('utf-8')))
-        else:
-            # It's a path on a network drive => 'file://host/share/a/b'
-            return 'file:' + urlquote_from_bytes(path.as_posix().encode('utf-8'))
-
 
 class _PosixFlavour(_Flavour):
     sep = '/'
@@ -253,12 +240,6 @@ def compile_pattern(self, pattern):
     def is_reserved(self, parts):
         return False
 
-    def make_uri(self, path):
-        # We represent the path using the local filesystem encoding,
-        # for portability to other applications.
-        bpath = bytes(path)
-        return 'file://' + urlquote_from_bytes(bpath)
-
 
 _windows_flavour = _WindowsFlavour()
 _posix_flavour = _PosixFlavour()
@@ -635,9 +616,7 @@ def __repr__(self):
 
     def as_uri(self):
         """Return the path as a 'file' URI."""
-        if not self.is_absolute():
-            raise ValueError("relative path can't be expressed as a file URI")
-        return self._flavour.make_uri(self)
+        return self._flavour.pathmod.fileuri(str(self))
 
     @property
     def _cparts(self):
diff --git a/Lib/posixpath.py b/Lib/posixpath.py
index 259baa64b193b8..e9e176303e9174 100644
--- a/Lib/posixpath.py
+++ b/Lib/posixpath.py
@@ -27,6 +27,7 @@
 import stat
 import genericpath
 from genericpath import *
+from urllib.parse import quote_from_bytes as urlquote
 
 __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
@@ -35,7 +36,7 @@
            "samefile","sameopenfile","samestat",
            "curdir","pardir","sep","pathsep","defpath","altsep","extsep",
            "devnull","realpath","supports_unicode_filenames","relpath",
-           "commonpath"]
+           "commonpath", "fileuri"]
 
 
 def _get_sep(path):
@@ -538,3 +539,19 @@ def commonpath(paths):
     except (TypeError, AttributeError):
         genericpath._check_arg_types('commonpath', *paths)
         raise
+
+
+def fileuri(path):
+    """
+    Return the given path expressed as a ``file://`` URI.
+    """
+
+    # We represent the path using the local filesystem encoding,
+    # for portability to other applications.
+    path = os.fspath(path)
+    if not isinstance(path, bytes):
+        path = os.fsencode(path)
+    if path[:1] == b'/':
+        return 'file://' + urlquote(path)
+    else:
+        raise ValueError("relative path can't be expressed as a file URI")
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 661c59d6171635..60155ff1ff7b95 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -786,6 +786,26 @@ def test_nt_helpers(self):
             self.assertIsInstance(b_final_path, bytes)
             self.assertGreater(len(b_final_path), 0)
 
+    def test_fileuri(self):
+        fn = ntpath.fileuri
+        self.assertEqual(fn('c:/'), 'file:///c:/')
+        self.assertEqual(fn('c:/a/b.c'), 'file:///c:/a/b.c')
+        self.assertEqual(fn('c:/a/b%#c'), 'file:///c:/a/b%25%23c')
+        self.assertEqual(fn('c:/a/b\xe9'), 'file:///c:/a/b%C3%A9')
+        self.assertEqual(fn('//some/share/'), 'file://some/share/')
+        self.assertEqual(fn('//some/share/a/b.c'), 'file://some/share/a/b.c')
+        self.assertEqual(fn('//some/share/a/b%#c\xe9'),
+                         'file://some/share/a/b%25%23c%C3%A9')
+
+        self.assertEqual(fn(b'c:/'), 'file:///c:/')
+        self.assertEqual(fn(b'c:/a/b.c'), 'file:///c:/a/b.c')
+        self.assertEqual(fn(b'c:/a/b%#c'), 'file:///c:/a/b%25%23c')
+        self.assertEqual(fn(b'c:/a/b\xc3\xa9'), 'file:///c:/a/b%C3%A9')
+        self.assertEqual(fn(b'//some/share/'), 'file://some/share/')
+        self.assertEqual(fn(b'//some/share/a/b.c'), 'file://some/share/a/b.c')
+        self.assertEqual(fn(b'//some/share/a/b%#c\xc3\xa9'),
+                         'file://some/share/a/b%25%23c%C3%A9')
+
 class NtCommonTest(test_genericpath.CommonTest, unittest.TestCase):
     pathmodule = ntpath
     attributes = ['relpath']
@@ -864,6 +884,12 @@ def test_path_commonpath(self):
     def test_path_isdir(self):
         self._check_function(self.path.isdir)
 
+    def test_path_fileuri(self):
+        file_name = 'C:\\foo\\bar'
+        file_path = FakePath(file_name)
+        self.assertPathEqual(
+            self.path.fileuri(file_name),
+            self.path.fileuri(file_path))
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/Lib/test/test_posixpath.py b/Lib/test/test_posixpath.py
index 8d398ec0103544..a934b90e6b967d 100644
--- a/Lib/test/test_posixpath.py
+++ b/Lib/test/test_posixpath.py
@@ -676,6 +676,15 @@ def check_error(exc, paths):
         self.assertRaises(TypeError, posixpath.commonpath,
                           ['usr/lib/', b'/usr/lib/python3'])
 
+    def test_fileuri(self):
+        self.assertEqual(posixpath.fileuri('/'), 'file:///')
+        self.assertEqual(posixpath.fileuri('/a/b.c'), 'file:///a/b.c')
+        self.assertEqual(posixpath.fileuri('/a/b%#c'), 'file:///a/b%25%23c')
+
+        self.assertEqual(posixpath.fileuri(b'/'), 'file:///')
+        self.assertEqual(posixpath.fileuri(b'/a/b.c'), 'file:///a/b.c')
+        self.assertEqual(posixpath.fileuri(b'/a/b%#c'), 'file:///a/b%25%23c')
+
 
 class PosixCommonTest(test_genericpath.CommonTest, unittest.TestCase):
     pathmodule = posixpath
@@ -752,6 +761,12 @@ def test_path_commonpath(self):
         common_path = self.path.commonpath([self.file_path, self.file_name])
         self.assertEqual(common_path, self.file_name)
 
+    def test_path_fileuri(self):
+        file_name = '/foo/bar'
+        file_path = FakePath(file_name)
+        self.assertEqual(
+            self.path.fileuri(file_name),
+            self.path.fileuri(file_path))
 
 if __name__=="__main__":
     unittest.main()
diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index 82f1d9dc2e7bb3..9914f6fb909c83 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -1663,7 +1663,7 @@ def test_non_ascii_drive_letter(self):
         self.assertRaises(IOError, url2pathname, "///\u00e8|/")
 
     def test_roundtrip_url2pathname(self):
-        list_of_paths = ['C:',
+        list_of_paths = ['C:\\',
                          r'\\\C\test\\',
                          r'C:\foo\bar\spam.foo'
                          ]
@@ -1673,16 +1673,13 @@ def test_roundtrip_url2pathname(self):
 class PathName2URLTests(unittest.TestCase):
 
     def test_converting_drive_letter(self):
-        self.assertEqual(pathname2url("C:"), '///C:')
-        self.assertEqual(pathname2url("C:\\"), '///C:')
+        self.assertEqual(pathname2url("C:\\"), '///C:/')
 
     def test_converting_when_no_drive_letter(self):
         self.assertEqual(pathname2url(r"\\\folder\test" "\\"),
-                         '/////folder/test/')
+                         '///folder/test/')
         self.assertEqual(pathname2url(r"\\folder\test" "\\"),
-                         '////folder/test/')
-        self.assertEqual(pathname2url(r"\folder\test" "\\"),
-                         '/folder/test/')
+                         '//folder/test/')
 
     def test_simple_compare(self):
         self.assertEqual(pathname2url(r'C:\foo\bar\spam.foo'),
@@ -1692,8 +1689,8 @@ def test_long_drive_letter(self):
         self.assertRaises(IOError, pathname2url, "XX:\\")
 
     def test_roundtrip_pathname2url(self):
-        list_of_paths = ['///C:',
-                         '/////folder/test/',
+        list_of_paths = ['///C:/',
+                         '//server/folder/test/',
                          '///C:/foo/bar/spam.foo']
         for path in list_of_paths:
             self.assertEqual(pathname2url(url2pathname(path)), path)
diff --git a/Misc/NEWS.d/next/Library/2021-06-13-17-35-24.bpo-44412.qFjsi6.rst b/Misc/NEWS.d/next/Library/2021-06-13-17-35-24.bpo-44412.qFjsi6.rst
new file mode 100644
index 00000000000000..adedbf3cc3791d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-06-13-17-35-24.bpo-44412.qFjsi6.rst
@@ -0,0 +1,2 @@
+Add :func:`os.path.fileuri` function that represents a file path as a
+``file://`` URI.