diff --git a/.changeset/light-dolls-pump.md b/.changeset/light-dolls-pump.md
new file mode 100644
index 0000000000..f421b152cb
--- /dev/null
+++ b/.changeset/light-dolls-pump.md
@@ -0,0 +1,5 @@
+---
+"stylelint": patch
+---
+
+Fixed: `selector-type-no-unknown` performance
diff --git a/lib/rules/selector-type-no-unknown/index.js b/lib/rules/selector-type-no-unknown/index.js
index 6f29bb862c..bb43695772 100644
--- a/lib/rules/selector-type-no-unknown/index.js
+++ b/lib/rules/selector-type-no-unknown/index.js
@@ -24,6 +24,8 @@ const meta = {
 	url: 'https://stylelint.io/user-guide/rules/selector-type-no-unknown',
 };
 
+const STARTS_A_TAG_NAME_REGEX = /(?:[^.#[:\w-]|^)\w/;
+
 /** @type {import('stylelint').Rule} */
 const rule = (primary, secondaryOptions) => {
 	return (root, result) => {
@@ -47,12 +49,13 @@ const rule = (primary, secondaryOptions) => {
 		}
 
 		root.walkRules((ruleNode) => {
-			const selector = ruleNode.selector;
-			const selectors = ruleNode.selectors;
+			const { selector } = ruleNode;
 
-			if (!isStandardSyntaxRule(ruleNode)) {
-				return;
-			}
+			if (!STARTS_A_TAG_NAME_REGEX.test(selector)) return;
+
+			if (!isStandardSyntaxRule(ruleNode)) return;
+
+			const { selectors } = ruleNode;
 
 			if (selectors.some((s) => isKeyframeSelector(s))) {
 				return;