diff --git a/.github/workflows/deploy-docs.yml b/.github/workflows/deploy-docs.yml
new file mode 100644
index 0000000..1373a27
--- /dev/null
+++ b/.github/workflows/deploy-docs.yml
@@ -0,0 +1,54 @@
+name: Deploy API Docs
+on:
+  push:
+    branches: [main]
+    paths:
+      - apollo-openapi.yaml
+      - redocly.yaml
+      - scripts/build-docs.sh
+      - package.json
+      - package-lock.json
+      - .github/workflows/deploy-docs.yml
+    tags: ['v*']
+  workflow_dispatch: {}
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      # Always build from main, never from the triggering ref: on a v* tag push
+      # github.ref is the tag, and site/next would then be built from the tag's
+      # spec instead of the current main HEAD. Released versions are read out of
+      # git history (git show <tag>:spec), so they are unaffected by this.
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          fetch-depth: 0
+          fetch-tags: true
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "20"
+      - run: npm ci
+      - run: ./scripts/build-docs.sh
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: site
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - id: deployment
+        uses: actions/deploy-pages@v4
diff --git a/.gitignore b/.gitignore
index 7146375..fe8a3f1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,9 @@
 
 # Temporary OpenAPI Generator output
 build/generated/
+
+# Node dependencies
+node_modules/
+
+# Generated docs site output
+site/
diff --git a/README.md b/README.md
index 1c6ffed..bb7b487 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,20 @@
 # apollo-openapi
 
 ![OpenAPI](https://img.shields.io/badge/spec-OpenAPI%203.0.1-blue)
+[![Docs](https://img.shields.io/badge/docs-API%20reference-blue)](https://apolloconfig.github.io/apollo-openapi/)
 
 This repository maintains the Apollo OpenAPI contract. The source of truth is
 [`apollo-openapi.yaml`](apollo-openapi.yaml).
 
+## 📖 API Reference
+
+Browse the rendered API reference for every released version (plus `next`
+for the unreleased `main` HEAD):
+
+**https://apolloconfig.github.io/apollo-openapi/**
+
+See [all versions](https://apolloconfig.github.io/apollo-openapi/versions.html).
+
 Generated code is treated as a temporary verification artifact, not as
 maintained source code or an official Apollo SDK. Apollo Portal pins a released
 `apollo-openapi.yaml` tag and generates its Spring OpenAPI interfaces during
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..9c6ba48
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,28 @@
+{
+  "name": "apollo-openapi-docs",
+  "lockfileVersion": 3,
+  "requires": true,
+  "packages": {
+    "": {
+      "name": "apollo-openapi-docs",
+      "devDependencies": {
+        "@redocly/cli": "2.51.2"
+      }
+    },
+    "node_modules/@redocly/cli": {
+      "version": "2.51.2",
+      "resolved": "https://registry.npmjs.org/@redocly/cli/-/cli-2.51.2.tgz",
+      "integrity": "sha512-pviW1gfsjCAuIVutmQcihlhlgoivfNzisBIR61EwSSREHGZ08Sbtjp/h/HPDkVavWwdzR/gs2wgHrdXLd6qU1A==",
+      "dev": true,
+      "license": "MIT",
+      "bin": {
+        "openapi": "bin/cli.js",
+        "redocly": "bin/cli.js"
+      },
+      "engines": {
+        "node": ">=22.12.0 || >=20.19.0 <21.0.0",
+        "npm": ">=10"
+      }
+    }
+  }
+}
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..95db336
--- /dev/null
+++ b/package.json
@@ -0,0 +1,11 @@
+{
+  "name": "apollo-openapi-docs",
+  "private": true,
+  "description": "Build tooling for the Apollo OpenAPI reference documentation site",
+  "scripts": {
+    "docs:build": "./scripts/build-docs.sh"
+  },
+  "devDependencies": {
+    "@redocly/cli": "2.51.2"
+  }
+}
diff --git a/redocly.yaml b/redocly.yaml
new file mode 100644
index 0000000..68f1e48
--- /dev/null
+++ b/redocly.yaml
@@ -0,0 +1,5 @@
+openapi:
+  theme:
+    colors:
+      primary:
+        main: '#1a56db'
diff --git a/scripts/build-docs.sh b/scripts/build-docs.sh
new file mode 100755
index 0000000..50e05e1
--- /dev/null
+++ b/scripts/build-docs.sh
@@ -0,0 +1,114 @@
+#!/bin/bash
+set -euo pipefail
+
+SPEC_FILE="${SPEC_FILE:-apollo-openapi.yaml}"
+SITE_DIR="${SITE_DIR:-site}"
+REDOCLY_VERSION="2.51.2"
+
+usage() {
+  cat <<'EOF'
+Usage: ./scripts/build-docs.sh [--help]
+
+Builds static Redoc HTML docs for every released git tag (vX.Y.Z) plus the
+current HEAD ("next") from apollo-openapi.yaml, into site/ (gitignored build
+output):
+
+  site/index.html        - copy of the latest successfully-built tag's docs
+  site/next/index.html    - built from the current working tree HEAD
+  site/vX.Y.Z/index.html  - one per released tag
+  site/versions.html      - generated index linking every built version
+
+Options:
+  --help    Show this help.
+EOF
+}
+
+for arg in "$@"; do
+  case "$arg" in
+    --help|-h)
+      usage
+      exit 0
+      ;;
+    *)
+      echo "Unknown argument: $arg" >&2
+      usage >&2
+      exit 2
+      ;;
+  esac
+done
+
+command -v npx >/dev/null 2>&1 || { echo "npx is required" >&2; exit 127; }
+REDOCLY=(npx --yes "@redocly/cli@${REDOCLY_VERSION}")
+
+WORK_DIR="$(mktemp -d)"
+trap 'rm -rf "$WORK_DIR"' EXIT
+
+echo "Cleaning previous site output..."
+rm -rf "$SITE_DIR"
+mkdir -p "$SITE_DIR"
+
+# build_one <spec-path> <title-label> <output-subdir>
+build_one() {
+  local spec_path="$1" label="$2" subdir="$3"
+  mkdir -p "$SITE_DIR/$subdir"
+  "${REDOCLY[@]}" build-docs "$spec_path" \
+    --output "$SITE_DIR/$subdir/index.html" \
+    --title "Apollo OpenAPI ($label)" \
+    --lint-config off
+}
+
+echo "Building next (unreleased HEAD)..."
+build_one "$SPEC_FILE" "next, unreleased" "next"
+
+TAGS=()
+while IFS= read -r tag; do
+  [ -n "$tag" ] && TAGS+=("$tag")
+done < <(git tag -l 'v*' --sort=v:refname)
+if [ "${#TAGS[@]}" -eq 0 ]; then
+  echo "No vX.Y.Z tags found" >&2
+  exit 1
+fi
+
+BUILT_TAGS=()
+for tag in "${TAGS[@]}"; do
+  echo "Building $tag..."
+  if ! git show "$tag:$SPEC_FILE" > "$WORK_DIR/$tag.yaml" 2>/dev/null; then
+    echo "WARN: $tag does not contain $SPEC_FILE, skipping" >&2
+    continue
+  fi
+  if build_one "$WORK_DIR/$tag.yaml" "$tag" "$tag"; then
+    BUILT_TAGS+=("$tag")
+  else
+    echo "WARN: build-docs failed for $tag, exit" >&2
+    exit 1
+  fi
+done
+
+if [ "${#BUILT_TAGS[@]}" -eq 0 ]; then
+  echo "No tag built successfully" >&2
+  exit 1
+fi
+
+LATEST_TAG="${BUILT_TAGS[${#BUILT_TAGS[@]}-1]}"
+echo "Latest version: $LATEST_TAG"
+cp "$SITE_DIR/$LATEST_TAG/index.html" "$SITE_DIR/index.html"
+
+echo "Generating versions.html..."
+{
+  echo '<!doctype html><html lang="en"><head><meta charset="utf-8">'
+  echo '<title>Apollo OpenAPI &mdash; Versions</title></head><body>'
+  echo '<h1>Apollo OpenAPI &mdash; Versions</h1>'
+  echo '<ul>'
+  echo "<li><a href=\"./next/\">next (unreleased, main HEAD)</a></li>"
+  for ((i = ${#BUILT_TAGS[@]} - 1; i >= 0; i--)); do
+    tag="${BUILT_TAGS[$i]}"
+    if [ "$tag" = "$LATEST_TAG" ]; then
+      echo "<li><a href=\"./$tag/\">$tag (latest)</a></li>"
+    else
+      echo "<li><a href=\"./$tag/\">$tag</a></li>"
+    fi
+  done
+  echo '</ul></body></html>'
+} > "$SITE_DIR/versions.html"
+
+echo "Done. Built $((${#BUILT_TAGS[@]} + 1)) versions (${#BUILT_TAGS[@]} tags + next)."