diff --git a/changelogs/fragments/84384-fix-undefined-key-host-group-vars.yml b/changelogs/fragments/84384-fix-undefined-key-host-group-vars.yml
new file mode 100644
index 00000000000..00f7117d802
--- /dev/null
+++ b/changelogs/fragments/84384-fix-undefined-key-host-group-vars.yml
@@ -0,0 +1,4 @@
+# Filename: changelogs/fragments/84384-fix-undefined-key-host-group-vars.yml
+
+bugfixes:
+  - host_group_vars - fixed defining the 'key' variable if the get_vars method is called with cache=False (https://github.com/ansible/ansible/issues/84384)
diff --git a/lib/ansible/plugins/vars/host_group_vars.py b/lib/ansible/plugins/vars/host_group_vars.py
index cb5b4b0c2b1..7baa76bf28f 100644
--- a/lib/ansible/plugins/vars/host_group_vars.py
+++ b/lib/ansible/plugins/vars/host_group_vars.py
@@ -119,21 +119,19 @@ class VarsModule(BaseVarsPlugin):
                     else:
                         raise AnsibleParserError("Supplied entity must be Host or Group, got %s instead" % (type(entity)))
 
-                    if cache:
-                        try:
-                            opath = PATH_CACHE[(realpath_basedir, subdir)]
-                        except KeyError:
-                            opath = PATH_CACHE[(realpath_basedir, subdir)] = os.path.join(realpath_basedir, subdir)
+                    try:
+                        opath = PATH_CACHE[(realpath_basedir, subdir)]
+                    except KeyError:
+                        opath = PATH_CACHE[(realpath_basedir, subdir)] = os.path.join(realpath_basedir, subdir)
+
+                    key = '%s.%s' % (entity_name, opath)
 
+                    if cache:
                         if opath in NAK:
                             continue
-                        key = '%s.%s' % (entity_name, opath)
                         if key in FOUND:
                             data = self.load_found_files(loader, data, FOUND[key])
                             continue
-                    else:
-                        opath = PATH_CACHE[(realpath_basedir, subdir)] = os.path.join(realpath_basedir, subdir)
-
                     if os.path.isdir(opath):
                         self._display.debug("\tprocessing dir %s" % opath)
                         FOUND[key] = found_files = loader.find_vars_files(opath, entity_name)