Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.

aggregator_theme in core/modules/aggregator/aggregator.module
Implements hook_theme().
block_content_theme in core/modules/block_content/block_content.module
Implements hook_theme().
block_theme in core/modules/block/block.module
Implements hook_theme().
book_theme in core/modules/book/book.module
Implements hook_theme().
ckeditor_theme in core/modules/ckeditor/ckeditor.module
Implements hook_theme().
color_theme in core/modules/color/color.module
Implements hook_theme().
comment_theme in core/modules/comment/comment.module
Implements hook_theme().
common_test_theme in core/modules/system/tests/modules/common_test/common_test.module
Implements hook_theme().
config_translation_theme in core/modules/config_translation/config_translation.module
Implements hook_theme().
content_moderation_theme in core/modules/content_moderation/content_moderation.module
Implements hook_theme().
drupal_common_theme in core/includes/theme.inc
Provides theme registration for themes across .inc files.
drupal_maintenance_theme in core/includes/bootstrap.inc
Enables use of the theme system without requiring database access.
field_ui_theme in core/modules/field_ui/field_ui.module
Implements hook_theme().
file_theme in core/modules/file/file.module
Implements hook_theme().
filter_theme in core/modules/filter/filter.module
Implements hook_theme().
forum_theme in core/modules/forum/forum.module
Implements hook_theme().
help_theme in core/modules/help/help.module
Implements hook_theme().
image_theme in core/modules/image/image.module
Implements hook_theme().
language_theme in core/modules/language/language.module
Implements hook_theme().
link_theme in core/modules/link/link.module
Implements hook_theme().
locale_test_theme in core/modules/locale/tests/modules/locale_test/locale_test.module
Implements hook_theme().
locale_theme in core/modules/locale/locale.module
Implements hook_theme().
node_theme in core/modules/node/node.module
Implements hook_theme().
nyan_cat_theme in core/modules/system/tests/themes/engines/nyan_cat/nyan_cat.engine
Implements hook_theme().
outside_in_theme in core/modules/outside_in/outside_in.module
Implements hook_theme().
rdf_theme in core/modules/rdf/rdf.module
Implements hook_theme().
responsive_image_theme in core/modules/responsive_image/responsive_image.module
Implements hook_theme().
search_theme in core/modules/search/search.module
Implements hook_theme().
simpletest_theme in core/modules/simpletest/simpletest.module
Implements hook_theme().
system_theme in core/modules/system/system.module
Implements hook_theme().
taxonomy_theme in core/modules/taxonomy/taxonomy.module
Implements hook_theme().
theme_suggestions_test_theme in core/modules/system/tests/modules/theme_suggestions_test/theme_suggestions_test.module
Implements hook_theme().
theme_test_theme in core/modules/system/tests/modules/theme_test/theme_test.module
Implements hook_theme().
toolbar_theme in core/modules/toolbar/toolbar.module
Implements hook_theme().
twig_extension_test_theme in core/modules/system/tests/modules/twig_extension_test/twig_extension_test.module
Implements hook_theme().
twig_theme in core/themes/engines/twig/twig.engine
Implements hook_theme().
twig_theme_test_theme in core/modules/system/tests/modules/twig_theme_test/twig_theme_test.module
Implements hook_theme().
update_theme in core/modules/update/update.module
Implements hook_theme().
user_theme in core/modules/user/user.module
Implements hook_theme().
views_theme in core/modules/views/views.module
Implements hook_theme().
views_ui_theme in core/modules/views_ui/views_ui.module
Implements hook_theme().