diff --git a/Lib/modulefinder.py b/Lib/modulefinder.py
--- a/Lib/modulefinder.py
+++ b/Lib/modulefinder.py
@@ -182,8 +182,8 @@ class ModuleFinder:
             if q:
                 self.msgout(4, "find_head_package ->", (q, tail))
                 return q, tail
-        self.msgout(4, "raise ImportError: No module named", qname)
-        raise ImportError("No module named " + qname)
+        self.msgout(4, "raise ImportError: No module named %r" % qname)
+        raise ImportError("No module named %r" % qname)
 
     def load_tail(self, q, tail):
         self.msgin(4, "load_tail", q, tail)
@@ -195,8 +195,8 @@ class ModuleFinder:
             mname = "%s.%s" % (m.__name__, head)
             m = self.import_module(head, mname, m)
             if not m:
-                self.msgout(4, "raise ImportError: No module named", mname)
-                raise ImportError("No module named " + mname)
+                self.msgout(4, "raise ImportError: No module named %r" % mname)
+                raise ImportError("No module named %r" % mname)
         self.msgout(4, "load_tail ->", m)
         return m
 
@@ -212,7 +212,7 @@ class ModuleFinder:
                 subname = "%s.%s" % (m.__name__, sub)
                 submod = self.import_module(sub, subname, m)
                 if not submod:
-                    raise ImportError("No module named " + subname)
+                    raise ImportError("No module named %r" % subname)
 
     def find_all_submodules(self, m):
         if not m.__path__:
diff --git a/Lib/runpy.py b/Lib/runpy.py
--- a/Lib/runpy.py
+++ b/Lib/runpy.py
@@ -101,19 +101,19 @@ def _get_filename(loader, mod_name):
 def _get_module_details(mod_name):
     loader = get_loader(mod_name)
     if loader is None:
-        raise ImportError("No module named %s" % mod_name)
+        raise ImportError("No module named %r" % mod_name)
     if loader.is_package(mod_name):
         if mod_name == "__main__" or mod_name.endswith(".__main__"):
-            raise ImportError("Cannot use package as __main__ module")
+            raise ImportError("Cannot use package as '__main__' module")
         try:
             pkg_main_name = mod_name + ".__main__"
             return _get_module_details(pkg_main_name)
         except ImportError as e:
             raise ImportError(("%s; %r is a package and cannot " +
-                               "be directly executed") %(e, mod_name))
+                               "be directly executed") % (e, mod_name))
     code = loader.get_code(mod_name)
     if code is None:
-        raise ImportError("No code object available for %s" % mod_name)
+        raise ImportError("No code object available for %r" % mod_name)
     filename = _get_filename(loader, mod_name)
     return mod_name, loader, code, filename
 
diff --git a/Lib/test/test_cmd_line_script.py b/Lib/test/test_cmd_line_script.py
--- a/Lib/test/test_cmd_line_script.py
+++ b/Lib/test/test_cmd_line_script.py
@@ -226,7 +226,7 @@ class CmdLineTest(unittest.TestCase):
             make_pkg(pkg_dir)
             main_dir = os.path.join(pkg_dir, '__main__')
             make_pkg(main_dir)
-            msg = ("Cannot use package as __main__ module; "
+            msg = ("Cannot use package as '__main__' module; "
                    "'test_pkg' is a package and cannot "
                    "be directly executed")
             launch_name = _make_launch_script(script_dir, 'launch', 'test_pkg')
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -271,6 +271,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #8754: Module names are now quoted (using repr) in all ImportError-like
+  messages emitted in the standard library.
+
 - Issue #12636: IDLE reads the coding cookie when executing a Python script.
 
 - Issue #12494: On error, call(), check_call(), check_output() and