diff --git a/lib/pr_checker.js b/lib/pr_checker.js
index 5e41eb8b..c743ddfe 100644
--- a/lib/pr_checker.js
+++ b/lib/pr_checker.js
@@ -26,6 +26,14 @@ const WAIT_TIME_SINGLE_APPROVAL = 24 * 7;
 const GITHUB_SUCCESS_CONCLUSIONS = ['SUCCESS', 'NEUTRAL', 'SKIPPED'];
 const GITHUB_ACTIONS_APP = 'github-actions';
 
+// https://github.com/nodejs/node/blob/main/doc/contributing/large-pull-requests.md
+const LARGE_PR_LINE_THRESHOLD = 5000;
+const LARGE_PR_REQUIRED_TSC_APPROVALS = 2;
+// Labels marking pull requests the large pull request policy does not apply
+// to. Routine dependency updates are excluded by the policy, and release
+// proposals are machine-generated and follow the release process instead.
+const LARGE_PR_EXEMPT_LABELS = ['dependencies', 'release'];
+
 const FAST_TRACK_RE = /^Fast-track has been requested by @(.+?)\. Please 👍 to approve\.$/;
 const FAST_TRACK_MIN_APPROVALS = 2;
 const GIT_CONFIG_GUIDE_URL = 'https://github.com/nodejs/node/blob/99b1ada/doc/guides/contributing/pull-requests.md#step-1-fork';
@@ -43,6 +51,7 @@ export const PR_CHECK_REASON_CODES = Object.freeze({
   MISSING_FULL_JENKINS_CI: 'missing-full-jenkins-ci',
   MISSING_GITHUB_CI: 'missing-github-ci',
   MISSING_JENKINS_CI: 'missing-jenkins-ci',
+  MISSING_LARGE_PR_TSC_APPROVAL: 'missing-large-pr-tsc-approval',
   MISSING_TSC_APPROVAL: 'missing-tsc-approval',
   NEW_CONTRIBUTOR: 'new-contributor',
   NO_COMMITS: 'no-commits',
@@ -139,6 +148,31 @@ export default class PRChecker {
       .map((p) => p.reviewer.login);
   }
 
+  // Net change in lines, as the large pull request policy counts it. Returns
+  // undefined when the data is not available, so callers can tell "not large"
+  // apart from "cannot tell".
+  getNetLineChange() {
+    const { additions, deletions } = this.pr;
+
+    if (typeof additions !== 'number' || typeof deletions !== 'number') {
+      return undefined;
+    }
+
+    return additions - deletions;
+  }
+
+  // Whether the pull request falls into one of the categories the large pull
+  // request policy exempts. Only the categories that can be told apart from
+  // the pull request data alone are covered here: the remaining ones (routine
+  // dependency updates, WPT imports, bot-issued pull requests, test-only
+  // refactors) need a judgement this cannot make, which is why a suspected
+  // large pull request is reported rather than blocked outright.
+  isExemptFromLargePRPolicy() {
+    const labels = this.pr.labels?.nodes?.map((l) => l.name) ?? [];
+
+    return LARGE_PR_EXEMPT_LABELS.some((label) => labels.includes(label));
+  }
+
   formatReview(reviewer, review) {
     let hint = '';
     if (reviewer.isTSC()) {
@@ -221,6 +255,38 @@ export default class PRChecker {
       }
     }
 
+    const netLineChange = this.getNetLineChange();
+    const isLargePR = netLineChange > LARGE_PR_LINE_THRESHOLD;
+
+    // A semver-major pull request has already been held to the same approval
+    // requirement above, so only check the ones that have not been.
+    if (isLargePR && !isSemverMajor) {
+      const tscApproved = this.getTSC(approved);
+
+      if (this.isExemptFromLargePRPolicy()) {
+        cli.info(
+          `This PR changes ${netLineChange} lines, but is exempt from the ` +
+          'large pull request policy'
+        );
+      } else if (tscApproved.length < LARGE_PR_REQUIRED_TSC_APPROVALS) {
+        const message = 'large pull requests require at least ' +
+          `${LARGE_PR_REQUIRED_TSC_APPROVALS} TSC approvals`;
+        cli.error(message);
+        cli.info(
+          `This PR changes ${netLineChange} lines, over the ` +
+          `${LARGE_PR_LINE_THRESHOLD} line threshold. See ` +
+          'https://github.com/nodejs/node/blob/main/doc/contributing/large-pull-requests.md'
+        );
+        this.addReason(
+          PR_CHECK_REASON_CODES.MISSING_LARGE_PR_TSC_APPROVAL, message, {
+            approvals: tscApproved.length,
+            required: LARGE_PR_REQUIRED_TSC_APPROVALS,
+            lines: netLineChange
+          });
+        return false;
+      }
+    }
+
     let fastTrackAppendix = '';
     if (isFastTracked) {
       const comment = [...this.comments].reverse().find((c) =>
diff --git a/lib/queries/PR.gql b/lib/queries/PR.gql
index 10400af4..ee52f593 100644
--- a/lib/queries/PR.gql
+++ b/lib/queries/PR.gql
@@ -57,6 +57,8 @@ query PR($prid: Int!, $owner: String!, $repo: String!) {
       baseRefName,
       headRefName,
       changedFiles,
+      additions,
+      deletions,
       mergeable,
       closed,
       closedAt,
diff --git a/test/fixtures/data.js b/test/fixtures/data.js
index c05b5d05..62bf5766 100644
--- a/test/fixtures/data.js
+++ b/test/fixtures/data.js
@@ -86,6 +86,8 @@ export const firstTimerPR = readJSON('first_timer_pr.json');
 export const firstTimerPrivatePR =
   readJSON('first_timer_pr_with_private_email.json');
 export const semverMajorPR = readJSON('semver_major_pr.json');
+export const largePR = readJSON('large_pr.json');
+export const largeExemptPR = readJSON('large_pr_exempt.json');
 export const fixAndRefPR = readJSON('pr_with_fixes_and_refs.json');
 export const fixCrossPR = readJSON('pr_with_fixes_cross.json');
 export const duplicateRefPR = readJSON('pr_with_duplicate_refs.json');
diff --git a/test/fixtures/large_pr.json b/test/fixtures/large_pr.json
new file mode 100644
index 00000000..4205a842
--- /dev/null
+++ b/test/fixtures/large_pr.json
@@ -0,0 +1,20 @@
+{
+  "createdAt": "2017-10-24T11:13:43Z",
+  "authorAssociation": "COLLABORATOR",
+  "author": {
+    "login": "pr_author",
+    "email": "pr_author@example.com",
+    "name": "Their Github Account email"
+  },
+  "url": "https://github.com/nodejs/node/pull/16438",
+  "bodyHTML": "<p>Awesome changes</p>",
+  "bodyText": "Awesome changes",
+  "labels": {
+    "nodes": []
+  },
+  "title": "lib: awesome changes",
+  "baseRefName": "main",
+  "headRefName": "awesome-changes",
+  "additions": 6000,
+  "deletions": 500
+}
diff --git a/test/fixtures/large_pr_exempt.json b/test/fixtures/large_pr_exempt.json
new file mode 100644
index 00000000..8e78d0d5
--- /dev/null
+++ b/test/fixtures/large_pr_exempt.json
@@ -0,0 +1,24 @@
+{
+  "createdAt": "2017-10-24T11:13:43Z",
+  "authorAssociation": "COLLABORATOR",
+  "author": {
+    "login": "pr_author",
+    "email": "pr_author@example.com",
+    "name": "Their Github Account email"
+  },
+  "url": "https://github.com/nodejs/node/pull/16438",
+  "bodyHTML": "<p>Awesome changes</p>",
+  "bodyText": "Awesome changes",
+  "labels": {
+    "nodes": [
+      {
+        "name": "dependencies"
+      }
+    ]
+  },
+  "title": "deps: update a dependency",
+  "baseRefName": "main",
+  "headRefName": "awesome-changes",
+  "additions": 6000,
+  "deletions": 500
+}
diff --git a/test/unit/pr_checker.test.js b/test/unit/pr_checker.test.js
index a64c4855..87753ec6 100644
--- a/test/unit/pr_checker.test.js
+++ b/test/unit/pr_checker.test.js
@@ -40,6 +40,8 @@ import {
   firstTimerPR,
   firstTimerPrivatePR,
   semverMajorPR,
+  largePR,
+  largeExemptPR,
   conflictingPR,
   closedPR,
   mergedPR,
@@ -61,6 +63,7 @@ const {
   MISSING_APPROVAL,
   MISSING_GITHUB_CI,
   MISSING_JENKINS_CI,
+  MISSING_LARGE_PR_TSC_APPROVAL,
   MISSING_TSC_APPROVAL,
   REQUESTED_CHANGES,
   STALE_REVIEW,
@@ -176,6 +179,132 @@ describe('PRChecker', () => {
       cli.assertCalledWith(expectedLogs);
     });
 
+    it('should error when a large PR has fewer than 2 TSC approvals', () => {
+      const cli = new TestCLI();
+
+      const expectedLogs = {
+        error: [
+          ['large pull requests require at least 2 TSC approvals']
+        ],
+        ok: [
+          ['Approvals: 4'],
+          ['- Foo User (@foo): https://github.com/nodejs/node/pull/16438#pullrequestreview-71480624'],
+          ['- Quux User (@Quux): LGTM'],
+          ['- Baz User (@Baz): https://github.com/nodejs/node/pull/16438#pullrequestreview-71488236'],
+          ['- Bar User (@bar) (TSC): lgtm']
+        ],
+        info: [
+          ['This PR was created on Fri, 23 Nov 2018 17:50:44 GMT'],
+          ['- Quux User (@Quux) approved in via LGTM in comments'],
+          ['- Bar User (@bar) approved in via LGTM in comments'],
+          ['This PR changes 5500 lines, over the 5000 line threshold. See ' +
+            'https://github.com/nodejs/node/blob/main/doc/contributing/large-pull-requests.md']
+        ]
+      };
+      const pr = Object.assign({}, largePR, {
+        createdAt: GT_7D
+      });
+
+      const data = {
+        pr,
+        reviewers: allGreenReviewers,
+        comments: commentsWithLGTM,
+        reviews: approvingReviews,
+        commits: simpleCommits,
+        collaborators,
+        authorIsNew: () => false,
+        getThread() {
+          return PRData.prototype.getThread.call(this);
+        }
+      };
+      const checker = new PRChecker(cli, data, {}, argv);
+
+      const status = checker.checkReviewsAndWait(new Date(NOW), true);
+      assert(!status);
+      assert.deepStrictEqual(checker.reasons, [{
+        code: MISSING_LARGE_PR_TSC_APPROVAL,
+        message: 'large pull requests require at least 2 TSC approvals',
+        approvals: 1,
+        required: 2,
+        lines: 5500
+      }]);
+      cli.assertCalledWith(expectedLogs);
+    });
+
+    it('should not require TSC approvals for an exempt large PR', () => {
+      const cli = new TestCLI();
+
+      const expectedLogs = {
+        ok: [
+          ['Approvals: 4'],
+          ['- Foo User (@foo): https://github.com/nodejs/node/pull/16438#pullrequestreview-71480624'],
+          ['- Quux User (@Quux): LGTM'],
+          ['- Baz User (@Baz): https://github.com/nodejs/node/pull/16438#pullrequestreview-71488236'],
+          ['- Bar User (@bar) (TSC): lgtm']
+        ],
+        info: [
+          ['This PR was created on Fri, 23 Nov 2018 17:50:44 GMT'],
+          ['- Quux User (@Quux) approved in via LGTM in comments'],
+          ['- Bar User (@bar) approved in via LGTM in comments'],
+          ['This PR changes 5500 lines, but is exempt from the large pull ' +
+            'request policy']
+        ]
+      };
+      const pr = Object.assign({}, largeExemptPR, {
+        createdAt: GT_7D
+      });
+
+      const data = {
+        pr,
+        reviewers: allGreenReviewers,
+        comments: commentsWithLGTM,
+        reviews: approvingReviews,
+        commits: simpleCommits,
+        collaborators,
+        authorIsNew: () => false,
+        getThread() {
+          return PRData.prototype.getThread.call(this);
+        }
+      };
+      const checker = new PRChecker(cli, data, {}, argv);
+
+      const status = checker.checkReviewsAndWait(new Date(NOW), true);
+      assert(status);
+      assert.deepStrictEqual(checker.reasons, []);
+      cli.assertCalledWith(expectedLogs);
+    });
+
+    it('should not apply the large PR check when the line counts are absent',
+      () => {
+        const cli = new TestCLI();
+
+        // Older fixtures, and any PR queried before `additions`/`deletions`
+        // were added to the query, carry no line counts.
+        const pr = Object.assign({}, largePR, {
+          createdAt: GT_7D,
+          additions: undefined,
+          deletions: undefined
+        });
+
+        const data = {
+          pr,
+          reviewers: allGreenReviewers,
+          comments: commentsWithLGTM,
+          reviews: approvingReviews,
+          commits: simpleCommits,
+          collaborators,
+          authorIsNew: () => false,
+          getThread() {
+            return PRData.prototype.getThread.call(this);
+          }
+        };
+        const checker = new PRChecker(cli, data, {}, argv);
+
+        const status = checker.checkReviewsAndWait(new Date(NOW), true);
+        assert(status);
+        assert.deepStrictEqual(checker.reasons, []);
+      });
+
     it('should error when PR has change requests', () => {
       const cli = new TestCLI();