diff --git a/.github/workflows/benchmark.yml b/.github/workflows/benchmark.yml
index 95893dca79..f98001dd61 100644
--- a/.github/workflows/benchmark.yml
+++ b/.github/workflows/benchmark.yml
@@ -24,7 +24,7 @@ jobs:
             - name: Setup Node
               uses: actions/setup-node@v4
               with:
-                  node-version: '20.18.1'
+                  node-version: '20.9.0' # earliest node version we support (via "engines" in package.json)
                   cache: 'yarn'
 
             - name: Install dependencies
diff --git a/.github/workflows/integration.yml b/.github/workflows/integration.yml
index d03a8386d1..54dcf73e2f 100644
--- a/.github/workflows/integration.yml
+++ b/.github/workflows/integration.yml
@@ -33,7 +33,7 @@ jobs:
             - name: Setup Node
               uses: actions/setup-node@v4
               with:
-                  node-version: '20.18.1'
+                  node-version: '20.9.0' # earliest node version we support (via "engines" in package.json)
                   cache: 'yarn'
 
             # Needed for local browser integration tests
diff --git a/.github/workflows/karma.yml b/.github/workflows/karma.yml
index 6d57464ad0..02b5d92ece 100644
--- a/.github/workflows/karma.yml
+++ b/.github/workflows/karma.yml
@@ -22,7 +22,7 @@ env:
     PUPPETEER_SKIP_DOWNLOAD: 'true' # only needed for @best/runner-local, unused here
     GITHUB_RUN_ID: ${{github.run_id}}
     COVERAGE: '1'
-    NODE_VERSION: '20.18.1'
+    NODE_VERSION: '20.9.0' # earliest node version we support (via "engines" in package.json)
 
 jobs:
     run-karma-tests-group-1:
diff --git a/.github/workflows/unit.yml b/.github/workflows/unit.yml
index defd1db8f4..9a85410dc6 100644
--- a/.github/workflows/unit.yml
+++ b/.github/workflows/unit.yml
@@ -29,7 +29,7 @@ jobs:
             - name: Setup Node
               uses: actions/setup-node@v4
               with:
-                  node-version: '20.18.1'
+                  node-version: '20.9.0' # earliest node version we support (via "engines" in package.json)
                   cache: 'yarn'
 
             # Needed for perf smoke tests, matches the chromedriver version installed by tachometer (https://github.com/google/tachometer/blob/main/README.md#on-demand-dependencies)
diff --git a/package.json b/package.json
index 0b98e31fe2..dae56ed7dc 100644
--- a/package.json
+++ b/package.json
@@ -86,11 +86,9 @@
         "packages/lwc",
         "playground"
     ],
-    "engines": {
-        "node": ">=10"
-    },
     "volta": {
-        "node": "20.18.1",
+        "//": "Earliest node version we support (via \"engines\" in package.json)",
+        "node": "20.9.0",
         "yarn": "1.22.22"
     },
     "resolutions": {
diff --git a/packages/@lwc/aria-reflection/package.json b/packages/@lwc/aria-reflection/package.json
index d0dd70fc0d..790e723732 100644
--- a/packages/@lwc/aria-reflection/package.json
+++ b/packages/@lwc/aria-reflection/package.json
@@ -26,6 +26,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/babel-plugin-component/package.json b/packages/@lwc/babel-plugin-component/package.json
index 24c62cbeaf..627c5677e6 100644
--- a/packages/@lwc/babel-plugin-component/package.json
+++ b/packages/@lwc/babel-plugin-component/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/compiler/package.json b/packages/@lwc/compiler/package.json
index abd56ce4c9..fe1c157b61 100644
--- a/packages/@lwc/compiler/package.json
+++ b/packages/@lwc/compiler/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/engine-core/package.json b/packages/@lwc/engine-core/package.json
index 94f70dc657..1d3456cf75 100644
--- a/packages/@lwc/engine-core/package.json
+++ b/packages/@lwc/engine-core/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/engine-dom/package.json b/packages/@lwc/engine-dom/package.json
index 4b7bc1ea82..6d00114676 100644
--- a/packages/@lwc/engine-dom/package.json
+++ b/packages/@lwc/engine-dom/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/engine-server/package.json b/packages/@lwc/engine-server/package.json
index ff01f82a86..1c33dd27c5 100644
--- a/packages/@lwc/engine-server/package.json
+++ b/packages/@lwc/engine-server/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/errors/package.json b/packages/@lwc/errors/package.json
index faa970971f..c60fa6edc9 100644
--- a/packages/@lwc/errors/package.json
+++ b/packages/@lwc/errors/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/features/package.json b/packages/@lwc/features/package.json
index df8375d977..b8832088fb 100644
--- a/packages/@lwc/features/package.json
+++ b/packages/@lwc/features/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/module-resolver/package.json b/packages/@lwc/module-resolver/package.json
index db909310ef..eb40c768f8 100644
--- a/packages/@lwc/module-resolver/package.json
+++ b/packages/@lwc/module-resolver/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/rollup-plugin/package.json b/packages/@lwc/rollup-plugin/package.json
index f63f45f08f..b3f50c116a 100644
--- a/packages/@lwc/rollup-plugin/package.json
+++ b/packages/@lwc/rollup-plugin/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/shared/package.json b/packages/@lwc/shared/package.json
index fd76a8c76d..2e5c39ffb0 100644
--- a/packages/@lwc/shared/package.json
+++ b/packages/@lwc/shared/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/signals/package.json b/packages/@lwc/signals/package.json
index 739da00f01..a6bb247a73 100644
--- a/packages/@lwc/signals/package.json
+++ b/packages/@lwc/signals/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/ssr-compiler/package.json b/packages/@lwc/ssr-compiler/package.json
index 5e8c0cd0b7..a56678b928 100644
--- a/packages/@lwc/ssr-compiler/package.json
+++ b/packages/@lwc/ssr-compiler/package.json
@@ -24,6 +24,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/ssr-runtime/package.json b/packages/@lwc/ssr-runtime/package.json
index ce700f77e5..472f665d0d 100644
--- a/packages/@lwc/ssr-runtime/package.json
+++ b/packages/@lwc/ssr-runtime/package.json
@@ -24,6 +24,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/style-compiler/package.json b/packages/@lwc/style-compiler/package.json
index faf5591082..50ce7a2b1e 100644
--- a/packages/@lwc/style-compiler/package.json
+++ b/packages/@lwc/style-compiler/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/synthetic-shadow/package.json b/packages/@lwc/synthetic-shadow/package.json
index 569e22a0d6..4275151ce0 100644
--- a/packages/@lwc/synthetic-shadow/package.json
+++ b/packages/@lwc/synthetic-shadow/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/template-compiler/package.json b/packages/@lwc/template-compiler/package.json
index 0e298213f9..5479e5655b 100644
--- a/packages/@lwc/template-compiler/package.json
+++ b/packages/@lwc/template-compiler/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/types/package.json b/packages/@lwc/types/package.json
index 1aa4d7f9e2..014a74b8ff 100644
--- a/packages/@lwc/types/package.json
+++ b/packages/@lwc/types/package.json
@@ -24,6 +24,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/packages/@lwc/wire-service/package.json b/packages/@lwc/wire-service/package.json
index d3f9d416fa..40bd7b2eb1 100644
--- a/packages/@lwc/wire-service/package.json
+++ b/packages/@lwc/wire-service/package.json
@@ -22,6 +22,9 @@
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=20.9.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
diff --git a/scripts/tasks/check-and-rewrite-package-json.js b/scripts/tasks/check-and-rewrite-package-json.js
index 25d6db1ed6..f05df3505e 100644
--- a/scripts/tasks/check-and-rewrite-package-json.js
+++ b/scripts/tasks/check-and-rewrite-package-json.js
@@ -106,6 +106,9 @@ for (const dir of globSync('./packages/@lwc/*')) {
         bugs: { url: 'https://github.com/salesforce/lwc/issues' },
         license: 'MIT',
         publishConfig: { access: 'public' },
+        engines: {
+            node: '>=20.9.0',
+        },
         // Use the same volta config in every subdirectory so that we always get the same node/yarn versions
         // See: https://docs.volta.sh/advanced/workspaces
         volta: {