Index: src/wp-includes/template.php
===================================================================
--- src/wp-includes/template.php	(revision 38418)
+++ src/wp-includes/template.php	(working copy)
@@ -189,6 +189,12 @@
 	$templates = array();
 
 	if ( ! empty( $category->slug ) ) {
+
+		$slug_decoded = urldecode( $category->slug );
+		if ( $slug_decoded !== $category->slug ) {
+			$templates[] = "category-{$slug_decoded}.php";
+		}
+
 		$templates[] = "category-{$category->slug}.php";
 		$templates[] = "category-{$category->term_id}.php";
 	}
@@ -219,6 +225,12 @@
 	$templates = array();
 
 	if ( ! empty( $tag->slug ) ) {
+
+		$slug_decoded = urldecode( $tag->slug );
+		if ( $slug_decoded !== $tag->slug ) {
+			$templates[] = "tag-{$slug_decoded}.php";
+		}
+
 		$templates[] = "tag-{$tag->slug}.php";
 		$templates[] = "tag-{$tag->term_id}.php";
 	}
@@ -255,6 +267,12 @@
 
 	if ( ! empty( $term->slug ) ) {
 		$taxonomy = $term->taxonomy;
+
+		$slug_decoded = urldecode( $term->slug );
+		if ( $slug_decoded !== $term->slug ) {
+			$templates[] = "taxonomy-$taxonomy-{$slug_decoded}.php";
+		}
+
 		$templates[] = "taxonomy-$taxonomy-{$term->slug}.php";
 		$templates[] = "taxonomy-$taxonomy.php";
 	}
@@ -349,8 +367,13 @@
 	$templates = array();
 	if ( $template && 0 === validate_file( $template ) )
 		$templates[] = $template;
-	if ( $pagename )
+	if ( $pagename ) {
+		$pagename_decoded = urldecode( $pagename );
+		if ( $pagename_decoded !== $pagename ) {
+			$templates[] = "page-{$pagename_decoded}.php";
+		}
 		$templates[] = "page-$pagename.php";
+	}
 	if ( $id )
 		$templates[] = "page-$id.php";
 	$templates[] = 'page.php';
@@ -409,6 +432,12 @@
 	$templates = array();
 
 	if ( ! empty( $object->post_type ) ) {
+
+		$name_decoded = urldecode( $object->post_name );
+		if ( $name_decoded !== $object->post_name ) {
+			$templates[] = "single-{$object->post_type}-{$name_decoded}.php";
+		}
+
 		$templates[] = "single-{$object->post_type}-{$object->post_name}.php";
 		$templates[] = "single-{$object->post_type}.php";
 	}
Index: tests/phpunit/tests/template.php
===================================================================
--- tests/phpunit/tests/template.php	(revision 38419)
+++ tests/phpunit/tests/template.php	(working copy)
@@ -16,23 +16,23 @@
 	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ) {
 		self::$page_on_front = $factory->post->create_and_get( array(
 			'post_type' => 'page',
-			'post_name' => 'page-on-front',
+			'post_name' => 'page-on-front-😀',
 		) );
 
 		self::$page_for_posts = $factory->post->create_and_get( array(
 			'post_type' => 'page',
-			'post_name' => 'page-for-posts',
+			'post_name' => 'page-for-posts-😀',
 		) );
 
 		self::$page = $factory->post->create_and_get( array(
 			'post_type' => 'page',
-			'post_name' => 'page-name',
+			'post_name' => 'page-name-😀',
 		) );
 		add_post_meta( self::$page->ID, '_wp_page_template', 'templates/page.php' );
 
 		self::$post = $factory->post->create_and_get( array(
 			'post_type' => 'post',
-			'post_name' => 'post-name',
+			'post_name' => 'post-name-😀',
 			'post_date' => '1984-02-25 12:34:56',
 		) );
 		set_post_format( self::$post, 'quote' );
@@ -84,11 +84,12 @@
 	public function test_category_template_hierarchy() {
 		$term = self::factory()->term->create_and_get( array(
 			'taxonomy' => 'category',
-			'slug'     => 'foo',
+			'slug'     => 'foo-😀',
 		) );
 
 		$this->assertTemplateHierarchy( get_term_link( $term ), array(
-			'category-foo.php',
+			'category-foo-😀.php',
+			'category-foo-%f0%9f%98%80.php',
 			"category-{$term->term_id}.php",
 			'category.php',
 			'archive.php',
@@ -98,11 +99,12 @@
 	public function test_tag_template_hierarchy() {
 		$term = self::factory()->term->create_and_get( array(
 			'taxonomy' => 'post_tag',
-			'slug'     => 'foo',
+			'slug'     => 'foo-😀',
 		) );
 
 		$this->assertTemplateHierarchy( get_term_link( $term ), array(
-			'tag-foo.php',
+			'tag-foo-😀.php',
+			'tag-foo-%f0%9f%98%80.php',
 			"tag-{$term->term_id}.php",
 			'tag.php',
 			'archive.php',
@@ -112,11 +114,12 @@
 	public function test_taxonomy_template_hierarchy() {
 		$term = self::factory()->term->create_and_get( array(
 			'taxonomy' => 'taxo',
-			'slug'     => 'foo',
+			'slug'     => 'foo-😀',
 		) );
 
 		$this->assertTemplateHierarchy( get_term_link( $term ), array(
-			'taxonomy-taxo-foo.php',
+			'taxonomy-taxo-foo-😀.php',
+			'taxonomy-taxo-foo-%f0%9f%98%80.php',
 			'taxonomy-taxo.php',
 			'taxonomy.php',
 			'archive.php',
@@ -170,7 +173,8 @@
 
 		$this->assertTemplateHierarchy( home_url(), array(
 			'front-page.php',
-			'page-page-on-front.php',
+			'page-page-on-front-😀.php',
+			'page-page-on-front-%f0%9f%98%80.php',
 			'page-' . self::$page_on_front->ID . '.php',
 			'page.php',
 			'singular.php',
@@ -191,7 +195,8 @@
 	public function test_page_template_hierarchy() {
 		$this->assertTemplateHierarchy( get_permalink( self::$page ), array(
 			'templates/page.php',
-			'page-page-name.php',
+			'page-page-name-😀.php',
+			'page-page-name-%f0%9f%98%80.php',
 			'page-' . self::$page->ID . '.php',
 			'page.php',
 			'singular.php',
@@ -200,7 +205,8 @@
 
 	public function test_single_template_hierarchy_for_post() {
 		$this->assertTemplateHierarchy( get_permalink( self::$post ), array(
-			'single-post-post-name.php',
+			'single-post-post-name-😀.php',
+			'single-post-post-name-%f0%9f%98%80.php',
 			'single-post.php',
 			'single.php',
 			'singular.php',
@@ -210,11 +216,12 @@
 	public function test_single_template_hierarchy_for_custom_post_type() {
 		$cpt = self::factory()->post->create_and_get( array(
 			'post_type' => 'cpt',
-			'post_name' => 'cpt-name',
+			'post_name' => 'cpt-name-😀',
 		) );
 
 		$this->assertTemplateHierarchy( get_permalink( $cpt ), array(
-			'single-cpt-cpt-name.php',
+			'single-cpt-cpt-name-😀.php',
+			'single-cpt-cpt-name-%f0%9f%98%80.php',
 			'single-cpt.php',
 			'single.php',
 			'singular.php',
@@ -223,7 +230,7 @@
 
 	public function test_attachment_template_hierarchy() {
 		$attachment = self::factory()->attachment->create_and_get( array(
-			'post_name'      => 'attachment-name',
+			'post_name'      => 'attachment-name-😀',
 			'file'           => 'image.jpg',
 			'post_mime_type' => 'image/jpeg',
 		) );
@@ -232,7 +239,8 @@
 			'jpeg.php',
 			'image.php',
 			'attachment.php',
-			'single-attachment-attachment-name.php',
+			'single-attachment-attachment-name-😀.php',
+			'single-attachment-attachment-name-%f0%9f%98%80.php',
 			'single-attachment.php',
 			'single.php',
 			'singular.php',
@@ -244,7 +252,8 @@
 			'embed-post-quote.php',
 			'embed-post.php',
 			'embed.php',
-			'single-post-post-name.php',
+			'single-post-post-name-😀.php',
+			'single-post-post-name-%f0%9f%98%80.php',
 			'single-post.php',
 			'single.php',
 			'singular.php',
@@ -256,7 +265,8 @@
 			'embed-page.php',
 			'embed.php',
 			'templates/page.php',
-			'page-page-name.php',
+			'page-page-name-😀.php',
+			'page-page-name-%f0%9f%98%80.php',
 			'page-' . self::$page->ID . '.php',
 			'page.php',
 			'singular.php',