diff --git a/CODEOWNERS b/CODEOWNERS
index 283b979289..0d5c319413 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -8,118 +8,118 @@ package.json @FrozenPandaz @vsavkin @AgentEnder @jaysoo @JamesHenry
 pnpm-lock.yaml @FrozenPandaz @vsavkin @AgentEnder @jaysoo @JamesHenry
 
 # Docs Site + Graph
-/docs @bcabanes @isaacplmann @juristr
-/docs/nx-cloud @StalkAltan @rarmatei @isaacplmann @juristr @bcabanes
+/docs @nrwl/nx-docs-reviewers
+/docs/nx-cloud @StalkAltan @rarmatei @nrwl/nx-docs-reviewers
 /graph/** @philipjfulcher @FrozenPandaz @bcabanes
-/images @bcabanes @isaacplmann @juristr
-/nx-dev/** @bcabanes @isaacplmann @juristr
-/typedoc-theme @bcabanes @isaacplmann
+/images @nrwl/nx-docs-reviewers
+/nx-dev/** @nrwl/nx-docs-reviewers
+/typedoc-theme @nrwl/nx-docs-reviewers
 
 # Plugin Verticals
 
 ## Angular
-/docs/generated/packages/angular/** @Coly010 @leosvelperez
-/docs/shared/packages/angular/** @Coly010 @leosvelperez @isaacplmann @juristr
-/packages/angular/** @Coly010 @leosvelperez
-/e2e/angular-core/** @Coly010 @leosvelperez
-/e2e/angular-extensions/** @Coly010 @leosvelperez
-/packages/angular/plugins/component-testing.ts @leosvelperez @Coly010 @barbados-clemens
-/packages/angular/src/generators/cypress-component-configuration/** @leosvelperez @Coly010 @barbados-clemens
-/packages/angular/src/generators/component-test/** @leosvelperez @Coly010 @barbados-clemens
+/docs/generated/packages/angular/** @nrwl/nx-angular-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/angular/** @nrwl/nx-angular-reviewers @nrwl/nx-docs-reviewers
+/packages/angular/** @nrwl/nx-angular-reviewers
+/e2e/angular-core/** @nrwl/nx-angular-reviewers
+/e2e/angular-extensions/** @nrwl/nx-angular-reviewers
+/packages/angular/plugins/component-testing.ts @nrwl/nx-angular-reviewers @nrwl/nx-testing-tools-reviewers
+/packages/angular/src/generators/cypress-component-configuration/** @nrwl/nx-angular-reviewers @nrwl/nx-testing-tools-reviewers
+/packages/angular/src/generators/component-test/** @nrwl/nx-angular-reviewers @nrwl/nx-testing-tools-reviewers
 
 ## React
-/docs/generated/packages/react/** @jaysoo @ndcunningham @mandarini @xiongemi
-/docs/generated/packages/next/** @jaysoo @ndcunningham @xiongemi
-/docs/shared/packages/react/** @jaysoo @ndcunningham @mandarini @xiongemi
-/docs/shared/packages/next/** @jaysoo @ndcunningham @xiongemi
-/packages/react/** @jaysoo @ndcunningham @mandarini @xiongemi
-/e2e/react-core/** @jaysoo @mandarini @xiongemi @ndcunningham
-/e2e/react-extensions/** @jaysoo @mandarini @xiongemi @ndcunningham
-/packages/next/** @ndcunningham @jaysoo @xiongemi
-/e2e/next/** @ndcunningham @jaysoo @xiongemi
-/packages/react/plugins/component-testing/** @jaysoo @ndcunningham @barbados-clemens
-/packages/react/src/generators/cypress-component-configuration/** @jaysoo @ndcunningham @barbados-clemens
-/packages/react/src/generators/component-test/** @jaysoo @ndcunningham @barbados-clemens
+/docs/generated/packages/react/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/next/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/react/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/next/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/packages/react/** @nrwl/nx-react-reviewers
+/e2e/react-core/** @nrwl/nx-react-reviewers
+/e2e/react-extensions/** @nrwl/nx-react-reviewers
+/packages/next/** @nrwl/nx-react-reviewers
+/e2e/next/** @nrwl/nx-react-reviewers
+/packages/react/plugins/component-testing/** @nrwl/nx-react-reviewers @nrwl/nx-testing-tools-reviewers
+/packages/react/src/generators/cypress-component-configuration/** @nrwl/nx-react-reviewers @nrwl/nx-testing-tools-reviewers
+/packages/react/src/generators/component-test/** @nrwl/nx-react-reviewers @nrwl/nx-testing-tools-reviewers
 
 # React Native
-/docs/generated/packages/detox/** @xiongemi @jaysoo @ndcunningham
-/docs/generated/packages/expo/** @xiongemi @jaysoo @ndcunningham
-/docs/generated/packages/react-native/** @xiongemi @jaysoo @ndcunningham
-/docs/shared/packages/react-native/** @xiongemi @jaysoo @ndcunningham @FrozenPandaz @isaacplmann @juristr
-/packages/detox/** @xiongemi @jaysoo @ndcunningham
-/e2e/detox/** @xiongemi @jaysoo @ndcunningham
-/packages/expo/** @xiongemi @jaysoo @ndcunningham
-/e2e/expo/** @xiongemi @jaysoo @ndcunningham
-/packages/react-native/** @xiongemi @jaysoo @ndcunningham
-/e2e/react-native/** @xiongemi @jaysoo @ndcunningham
+/docs/generated/packages/detox/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/expo/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/react-native/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/react-native/** @nrwl/nx-react-reviewers @nrwl/nx-docs-reviewers
+/packages/detox/** @nrwl/nx-react-reviewers
+/e2e/detox/** @nrwl/nx-react-reviewers
+/packages/expo/** @nrwl/nx-react-reviewers
+/e2e/expo/** @nrwl/nx-react-reviewers
+/packages/react-native/** @nrwl/nx-react-reviewers
+/e2e/react-native/** @nrwl/nx-react-reviewers
 
 ## Node
-/docs/generated/packages/node/** @nartc @ndcunningham @jaysoo
-/docs/generated/packages/nest/** @nartc @ndcunningham @jaysoo
-/docs/generated/packages/express/** @nartc @ndcunningham @jaysoo
-/docs/shared/packages/node/** @nartc @FrozenPandaz @isaacplmann @juristr
-/docs/shared/packages/express/** @ndcunningham @nartc @FrozenPandaz @isaacplmann @juristr
-/docs/shared/packages/nest/** @ndcunningham @nartc @FrozenPandaz @isaacplmann @juristr
-/packages/node/** @nartc @ndcunningham @jaysoo
-/packages/express/** @nartc @ndcunningham @jaysoo
-/packages/nest/** @nartc @ndcunningham @jaysoo
-/e2e/node/** @nartc @ndcunningham @jaysoo
+/docs/generated/packages/node/** @nrwl/nx-node-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/nest/** @nrwl/nx-node-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/express/** @nrwl/nx-node-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/node/** @nrwl/nx-node-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/express/** @nrwl/nx-node-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/nest/** @nrwl/nx-node-reviewers @FrozenPandaz @nrwl/nx-docs-reviewers
+/packages/node/** @nrwl/nx-node-reviewers
+/packages/express/** @nrwl/nx-node-reviewers
+/packages/nest/** @nrwl/nx-node-reviewers
+/e2e/node/** @nrwl/nx-node-reviewers
 
 ## JS
-/docs/generated/packages/js/** @nartc @jaysoo @ndcunningham
-/docs/generated/packages/web/** @jaysoo @mandarini @ndcunningham
-/docs/generated/packages/webpack/** @jaysoo @mandarini @ndcunningham
-/docs/generated/packages/esbuild/** @nartc @jaysoo @ndcunningham
-/docs/generated/packages/rollup/** @jaysoo @mandarini @ndcunningham
-/docs/generated/packages/vite/** @jaysoo @mandarini @ndcunningham
-/docs/shared/packages/js/** @nartc @jaysoo @ndcunningham
-/docs/shared/packages/web/** @jaysoo @mandarini @ndcunningham
-/docs/shared/packages/webpack/** @jaysoo @mandarini @ndcunningham
-/docs/shared/packages/esbuild/** @nartc @jaysoo @ndcunningham
-/docs/shared/packages/vite/** @jaysoo @mandarini @ndcunningham
-/packages/js/** @nartc @jaysoo @ndcunningham
-/e2e/js/** @nartc @jaysoo @ndcunningham
-/packages/web/** @jaysoo @mandarini @ndcunningham
-/e2e/web/** @jaysoo @mandarini @ndcunningham
-/packages/webpack/** @jaysoo @mandarini @ndcunningham
-/e2e/webpack/** @jaysoo @mandarini @ndcunningham
-/packages/esbuild/** @jaysoo @nartc @ndcunningham
-/e2e/esbuild/** @jaysoo @nartc @ndcunningham
-/packages/rollup/** @jaysoo @mandarini @ndcunningham
-/e2e/rollup/** @jaysoo @mandarini @ndcunningham
-/packages/vite/** @jaysoo @mandarini @ndcunningham
-/e2e/vite/** @jaysoo @mandarini @ndcunningham
+/docs/generated/packages/js/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/web/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/webpack/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/esbuild/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/rollup/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/vite/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/js/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/web/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/webpack/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/esbuild/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/vite/** @nrwl/nx-js-reviewers @nrwl/nx-docs-reviewers
+/packages/js/** @nrwl/nx-js-reviewers
+/e2e/js/** @nrwl/nx-js-reviewers
+/packages/web/** @nrwl/nx-js-reviewers
+/e2e/web/** @nrwl/nx-js-reviewers
+/packages/webpack/** @nrwl/nx-js-reviewers
+/e2e/webpack/** @nrwl/nx-js-reviewers
+/packages/esbuild/** @nrwl/nx-js-reviewers
+/e2e/esbuild/** @nrwl/nx-js-reviewers
+/packages/rollup/** @nrwl/nx-js-reviewers
+/e2e/rollup/** @nrwl/nx-js-reviewers
+/packages/vite/** @nrwl/nx-js-reviewers
+/e2e/vite/** @nrwl/nx-js-reviewers
 
 ## Tools
-/docs/generated/packages/cypress/** @barbados-clemens @FrozenPandaz
-/docs/generated/packages/jest/** @barbados-clemens @FrozenPandaz
-/docs/shared/packages/jest/** @barbados-clemens @FrozenPandaz @isaacplmann @juristr
-/docs/shared/packages/cypress/** @barbados-clemens @FrozenPandaz @isaacplmann @juristr
-/packages/cypress/** @barbados-clemens @FrozenPandaz
-/e2e/cypress/** @barbados-clemens @FrozenPandaz
-/packages/jest/** @barbados-clemens @FrozenPandaz
-/e2e/jest/** @barbados-clemens @FrozenPandaz
+/docs/generated/packages/cypress/** @nrwl/nx-testing-tools-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/jest/** @nrwl/nx-testing-tools-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/jest/** @nrwl/nx-testing-tools-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/cypress/** @nrwl/nx-testing-tools-reviewers @nrwl/nx-docs-reviewers
+/packages/cypress/** @nrwl/nx-testing-tools-reviewers
+/e2e/cypress/** @nrwl/nx-testing-tools-reviewers
+/packages/jest/** @nrwl/nx-testing-tools-reviewers
+/e2e/jest/** @nrwl/nx-testing-tools-reviewers
 
 # Linter
-/docs/generated/packages/eslint-plugin/** @meeroslav @FrozenPandaz @JamesHenry
-/docs/generated/packages/linter/** @meeroslav @FrozenPandaz @JamesHenry
-/docs/shared/packages/linter/** @meeroslav @FrozenPandaz @isaacplmann @juristr
-/packages/eslint-plugin/** @meeroslav @FrozenPandaz @JamesHenry
-/packages/linter/** @meeroslav @FrozenPandaz @JamesHenry
-/e2e/linter/** @meeroslav @FrozenPandaz
-.eslint* @meeroslav @FrozenPandaz @JamesHenry
+/docs/generated/packages/eslint-plugin/** @nrwl/nx-linter-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/linter/** @nrwl/nx-linter-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/linter/** @nrwl/nx-linter-reviewers @nrwl/nx-docs-reviewers
+/packages/eslint-plugin/** @nrwl/nx-linter-reviewers
+/packages/linter/** @nrwl/nx-linter-reviewers
+/e2e/linter/** @nrwl/nx-linter-reviewers
+.eslint* @nrwl/nx-linter-reviewers
 
 # Storybook
-/docs/generated/packages/storybook/** @mandarini @jaysoo @Coly010
-/docs/shared/packages/storybook/** @mandarini @jaysoo @Coly010
-/packages/storybook/** @mandarini @jaysoo @Coly010
-/e2e/storybook/** @mandarini @FrozenPandaz @Coly010
-/e2e/storybook-angular/** @mandarini @Coly010
+/docs/generated/packages/storybook/** @nrwl/nx-storybook-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/storybook/** @nrwl/nx-storybook-reviewers @nrwl/nx-docs-reviewers
+/packages/storybook/** @nrwl/nx-storybook-reviewers
+/e2e/storybook/** @nrwl/nx-storybook-reviewers
+/e2e/storybook-angular/** @nrwl/nx-storybook-reviewers
 
 ## Devkit
-/docs/generated/devkit/** @FrozenPandaz @AgentEnder
-/docs/generated/packages/devkit/** @FrozenPandaz @AgentEnder
-/packages/devkit/** @FrozenPandaz @AgentEnder
+/docs/generated/devkit/** @nrwl/nx-devkit-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/devkit/** @nrwl/nx-devkit-reviewers @nrwl/nx-docs-reviewers
+/packages/devkit/** @nrwl/nx-devkit-reviewers
 /packages/devkit/index.js @FrozenPandaz @vsavkin
 /packages/devkit/index.d.ts @FrozenPandaz @vsavkin
 /packages/devkit/public-api.ts @FrozenPandaz @vsavkin
@@ -127,32 +127,32 @@ pnpm-lock.yaml @FrozenPandaz @vsavkin @AgentEnder @jaysoo @JamesHenry
 /packages/devkit/src/utils/module-federation @jaysoo @Coly010
 
 # Nx-Plugin
-/docs/generated/packages/plugin/** @AgentEnder @FrozenPandaz
-/docs/shared/packages/plugin/** @AgentEnder @FrozenPandaz @isaacplmann @juristr
-/packages/plugin/** @AgentEnder @FrozenPandaz
-/e2e/plugin/** @AgentEnder @FrozenPandaz
+/docs/generated/packages/plugin/** @nrwl/nx-devkit-reviewers @nrwl/nx-docs-reviewers
+/docs/shared/packages/plugin/** @nrwl/nx-devkit-reviewers @nrwl/nx-docs-reviewers
+/packages/plugin/** @nrwl/nx-devkit-reviewers
+/e2e/plugin/** @nrwl/nx-devkit-reviewers
 
 ## Core
-/docs/generated/cli/** @vsavkin @FrozenPandaz @AgentEnder
-/docs/generated/packages/nx/** @vsavkin @FrozenPandaz @AgentEnder
-/docs/generated/packages/workspace/** @vsavkin @FrozenPandaz @AgentEnder
-/packages/nx/** @vsavkin @FrozenPandaz @AgentEnder
-/packages/nx/src/adapter @AgentEnder @leosvelperez
-/packages/nx/src/native @vsavkin @FrozenPandaz @Cammisuli
-/packages/nx/src/plugins/js/lock-file @meeroslav @FrozenPandaz
-/packages/nx/src/command-line/init/implementation/angular/** @Coly010 @leosvelperez @FrozenPandaz
-/e2e/nx-init/src/nx-init-angular.test.ts @Coly010 @leosvelperez
-/packages/nx/src/command-line/init/implementation/react/** @jaysoo @xiongemi @mandarini
-/e2e/nx-init/src/nx-init-react.test.ts @jaysoo @xiongemi @mandarini @ndcunningham
-/e2e/nx-init/src/files/cra/** @jaysoo @xiongemi @mandarini @ndcunningham
-/e2e/nx*/** @FrozenPandaz @AgentEnder @vsavkin
-/packages/workspace/** @FrozenPandaz @AgentEnder @vsavkin
-/e2e/workspace-create/** @FrozenPandaz @AgentEnder @vsavkin
-/e2e/workspace-create-npm/** @FrozenPandaz @vsavkin
+/docs/generated/cli/** @nrwl/nx-core-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/nx/** @nrwl/nx-core-reviewers @nrwl/nx-docs-reviewers
+/docs/generated/packages/workspace/** @nrwl/nx-core-reviewers @nrwl/nx-docs-reviewers
+/packages/nx/** @nrwl/nx-core-reviewers
+/packages/nx/src/adapter @nrwl/nx-core-reviewers @leosvelperez
+/packages/nx/src/native @nrwl/nx-core-reviewers @nrwl/nx-native-reviewers
+/packages/nx/src/plugins/js/lock-file @nrwl/nx-core-reviewers @meeroslav
+/packages/nx/src/command-line/init/implementation/angular/** @nrwl/nx-angular-reviewers @nrwl/nx-core-reviewers
+/e2e/nx-init/src/nx-init-angular.test.ts @nrwl/nx-angular-reviewers
+/packages/nx/src/command-line/init/implementation/react/** @nrwl/nx-react-reviewers
+/e2e/nx-init/src/nx-init-react.test.ts @nrwl/nx-react-reviewers
+/e2e/nx-init/src/files/cra/** @nrwl/nx-react-reviewers
+/e2e/nx*/** @nrwl/nx-core-reviewers
+/packages/workspace/** @nrwl/nx-core-reviewers
+/e2e/workspace-create/** @nrwl/nx-core-reviewers
+/e2e/workspace-create-npm/** @nrwl/nx-core-reviewers
 
 # Misc
 /e2e/lerna-smoke-tests/** @vsavkin @JamesHenry
-/e2e/utils/** @meeroslav @barbados-clemens @vsavkin @mandarini
+/e2e/utils/** @meeroslav @nrwl/nx-testing-tools-reviewers @vsavkin @mandarini
 /community @AgentEnder @FrozenPandaz
 /CONTRIBUTING.md @FrozenPandaz @isaacplmann
 /CODE_OF_CONDUCT.md @FrozenPandaz @isaacplmann
@@ -160,9 +160,9 @@ pnpm-lock.yaml @FrozenPandaz @vsavkin @AgentEnder @jaysoo @JamesHenry
 
 # Scripts
 /scripts/depcheck @FrozenPandaz @vsavkin @jaysoo
-/scripts/documentation @bcabanes @isaacplmann
+/scripts/documentation @nrwl/nx-docs-reviewers
 /scripts/local-registry @FrozenPandaz @vsavkin
-/scripts/angular-support-upgrades @Coly010 @leosvelperez
+/scripts/angular-support-upgrades @nrwl/nx-angular-reviewers
 
 # CI
 /.circleci/** @meeroslav @vsavkin @FrozenPandaz
@@ -172,9 +172,9 @@ pnpm-lock.yaml @FrozenPandaz @vsavkin @AgentEnder @jaysoo @JamesHenry
 
 # Global Files
 project.json @FrozenPandaz @vsavkin
-jest.config.ts @barbados-clemens @FrozenPandaz
-jest.preset.js @barbados-clemens @FrozenPandaz
+jest.config.ts @nrwl/nx-testing-tools-reviewers @FrozenPandaz
+jest.preset.js @nrwl/nx-testing-tools-reviewers @FrozenPandaz
 
 # Overrides - These are applied last, so override any matches above.
-docs/generated/manifests/* @bcabanes @FrozenPandaz @jaysoo @AgentEnder @isaacplmann @juristr
-docs/generated/packages-metadata.json @bcabanes @FrozenPandaz @jaysoo @AgentEnder @isaacplmann @juristr
+docs/generated/manifests/* @FrozenPandaz @jaysoo @AgentEnder @nrwl/nx-docs-reviewers
+docs/generated/packages-metadata.json @FrozenPandaz @jaysoo @AgentEnder @nrwl/nx-docs-reviewers
diff --git a/scripts/check-codeowners.ts b/scripts/check-codeowners.ts
index 73c16d6549..023b9829aa 100644
--- a/scripts/check-codeowners.ts
+++ b/scripts/check-codeowners.ts
@@ -1,7 +1,9 @@
 import * as fg from 'fast-glob';
 import * as path from 'path';
 import * as fs from 'fs';
+import * as octokit from 'octokit';
 import { output } from '@nx/devkit';
+import { Octokit } from 'octokit';
 
 async function main() {
   const codeowners = fs.readFileSync(
@@ -12,13 +14,19 @@ async function main() {
     .split('\n')
     .filter((line) => line.trim().length > 0 && !line.startsWith('#'));
 
-  const errors: string[] = [];
+  const mismatchedPatterns: string[] = [];
+  const mismatchedOwners: string[] = [];
+
+  const gh = new octokit.Octokit({
+    auth: process.env.GITHUB_TOKEN,
+  }).rest;
+  const cache: Map<string, boolean> = new Map();
 
   for (const line of codeownersLines) {
     // This is perhaps a bit naive, but it should
     // work for all paths and patterns that do not
     // contain spaces.
-    const specifiedPattern = line.split(' ')[0];
+    const [specifiedPattern, ...owners] = line.split(' ');
     let foundMatchingFiles = false;
 
     const patternsToCheck = specifiedPattern.startsWith('/')
@@ -34,16 +42,85 @@ async function main() {
         }).length > 0;
     }
     if (!foundMatchingFiles) {
-      errors.push(specifiedPattern);
+      mismatchedPatterns.push(specifiedPattern);
+    }
+
+    if (process.env.GITHUB_TOKEN) {
+      for (let owner of owners) {
+        owner = owner.substring(1); // Remove the @
+        if (owner.includes('/')) {
+          // Its a team.
+          const [org, team] = owner.split('/');
+          let res = cache.get(owner);
+          if (res === undefined) {
+            res = await validateTeam(gh, org, team);
+            cache.set(owner, res);
+          }
+          if (res === false) {
+            mismatchedOwners.push(`${specifiedPattern}: ${owner}`);
+          }
+        } else {
+          let res = cache.get(owner);
+          if (res === undefined) {
+            res = await validateUser(gh, owner);
+            cache.set(owner, res);
+          }
+          if (res === false) {
+            mismatchedOwners.push(`${specifiedPattern}: ${owner}`);
+          }
+        }
+      }
+    } else {
+      output.warn({
+        title: `Skipping owner validation because GITHUB_TOKEN is not set.`,
+      });
     }
   }
-  if (errors.length > 0) {
+  if (mismatchedPatterns.length > 0) {
     output.error({
       title: `The following patterns in CODEOWNERS do not match any files:`,
-      bodyLines: errors.map((e) => `- ${e}`),
+      bodyLines: mismatchedPatterns.map((e) => `- ${e}`),
     });
-    process.exit(1);
   }
+
+  if (mismatchedOwners.length > 0) {
+    output.error({
+      title: `The following owners in CODEOWNERS do not exist:`,
+      bodyLines: mismatchedOwners.map((e) => `- ${e}`),
+    });
+  }
+
+  process.exit(mismatchedPatterns.length + mismatchedOwners.length > 0 ? 1 : 0);
 }
 
 main();
+
+async function validateTeam(
+  gh: Octokit['rest'],
+  org: string,
+  team: string
+): Promise<boolean> {
+  try {
+    await gh.teams.getByName({
+      org,
+      team_slug: team,
+    });
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+async function validateUser(
+  gh: Octokit['rest'],
+  username: string
+): Promise<boolean> {
+  try {
+    await gh.users.getByUsername({
+      username,
+    });
+    return true;
+  } catch {
+    return false;
+  }
+}