diff --git a/.github/workflows/ruby.yml b/.github/workflows/ruby.yml
index e4fa205c..032b48d4 100644
--- a/.github/workflows/ruby.yml
+++ b/.github/workflows/ruby.yml
@@ -27,7 +27,21 @@ jobs:
       matrix:
         ruby: [ '3.2', '3.3', '3.4', '4.0' ]
         gemfile: [rails.7.2.activerecord, rails.8.0.activerecord, rails.8.1.activerecord]
-    name: ${{ matrix.ruby }}-${{ matrix.gemfile }}
+        elasticsearch: ['9.4.3']
+        include:
+          - ruby: '3.3'
+            gemfile: rails.7.2.activerecord
+            elasticsearch: '8.19.3'
+            es_gem_constraint: '~> 8.14'
+          - ruby: '3.4'
+            gemfile: rails.8.0.activerecord
+            elasticsearch: '8.19.3'
+            es_gem_constraint: '~> 8.14'
+          - ruby: '4.0'
+            gemfile: rails.8.1.activerecord
+            elasticsearch: '8.19.3'
+            es_gem_constraint: '~> 8.14'
+    name: ${{ matrix.ruby }}-${{ matrix.gemfile }}-es${{ matrix.elasticsearch }}
 
     env:
       BUNDLE_GEMFILE: gemfiles/${{ matrix.gemfile }}.gemfile
@@ -45,7 +59,7 @@ jobs:
           --health-timeout 5s
           --health-retries 5
       elasticsearch:
-        image: docker.elastic.co/elasticsearch/elasticsearch:8.19.13
+        image: docker.elastic.co/elasticsearch/elasticsearch:${{ matrix.elasticsearch }}
         ports:
           - '9250:9200'
         env:
@@ -61,6 +75,9 @@ jobs:
 
     steps:
       - uses: actions/checkout@v7
+      - name: Pin elasticsearch gem for ES 8.x
+        if: matrix.es_gem_constraint
+        run: echo "gem 'elasticsearch', '${{ matrix.es_gem_constraint }}'" >> $BUNDLE_GEMFILE
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby }}
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 85a38efa..2f2f0a2d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,9 @@
 
 ### Changes
 
+* [#1009](https://github.com/toptal/chewy/pull/1009): **(Breaking)** Add Elasticsearch 9.x support while retaining ES 8.x compatibility. The `elasticsearch` gem dependency now allows `>= 8.14, < 10.0`. ([@mattmenefee][])
+  * The `search_query.chewy` notification payload for scroll requests now nests `scroll_id` under `body:` (i.e. `{scroll: '1m', body: {scroll_id: '...'}}` instead of `{scroll: '1m', scroll_id: '...'}`). Update any application code that subscribes to scroll notification payloads.
+
 ## 8.4.1 (2026-06-19)
 
 ### New Features
diff --git a/README.md b/README.md
index c3f4e938..2a458818 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,7 @@ Chewy is compatible with MRI 3.2-4.0.
 
 | Chewy version | Elasticsearch version              |
 | ------------- | ---------------------------------- |
+| 9.0.x         | 8.x, 9.x                           |
 | 8.0.x         | 8.x                                |
 | 7.2.x         | 7.x                                |
 | 7.1.x         | 7.x                                |
diff --git a/chewy.gemspec b/chewy.gemspec
index 57aba403..bf538548 100644
--- a/chewy.gemspec
+++ b/chewy.gemspec
@@ -18,7 +18,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_dependency 'activesupport', '>= 7.2'
-  spec.add_dependency 'elasticsearch', '>= 8.14', '< 9.0'
+  spec.add_dependency 'elasticsearch', '>= 8.14', '< 10.0'
   spec.add_dependency 'elasticsearch-dsl'
   spec.metadata['rubygems_mfa_required'] = 'true'
 end
diff --git a/docker-compose.yml b/docker-compose.yml
index 690cc53c..64403c79 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,6 +1,6 @@
 services:
   elasticsearch_test:
-    image: "docker.elastic.co/elasticsearch/elasticsearch:${ES_VERSION:-8.19.13}"
+    image: "docker.elastic.co/elasticsearch/elasticsearch:${ES_VERSION:-9.4.3}"
     environment:
       - bootstrap.memory_lock=${ES_MEMORY_LOCK:-false}
       - "ES_JAVA_OPTS=-Xms${TEST_ES_HEAP_SIZE:-500m} -Xmx${TEST_ES_HEAP_SIZE:-500m}"
diff --git a/lib/chewy/search/scrolling.rb b/lib/chewy/search/scrolling.rb
index de505d11..d906eddc 100644
--- a/lib/chewy/search/scrolling.rb
+++ b/lib/chewy/search/scrolling.rb
@@ -136,9 +136,10 @@ def scroll_objects(**options, &block)
 
     private
 
-      def perform_scroll(body)
-        ActiveSupport::Notifications.instrument 'search_query.chewy', notification_payload(request: body) do
-          Chewy.client.scroll(body)
+      def perform_scroll(scroll:, scroll_id:)
+        request = {scroll: scroll, body: {scroll_id: scroll_id}}
+        ActiveSupport::Notifications.instrument 'search_query.chewy', notification_payload(request: request) do
+          Chewy.client.scroll(request)
         end
       end
     end
diff --git a/migration_guide.md b/migration_guide.md
index 5f53359e..91951b0e 100644
--- a/migration_guide.md
+++ b/migration_guide.md
@@ -4,6 +4,46 @@ This document outlines the steps you need to take when migrating between major v
 Chewy and Elasticsearch. For simplicity's sake the guide will assume that you're using
 Chewy alongside a matching Elasticsearch version.
 
+## Chewy 8/Elasticsearch 8 to Chewy 9/Elasticsearch 9
+
+The Chewy 8 to 9 upgrade is relatively straightforward compared to previous major versions.
+The primary changes concern the `elasticsearch` Ruby gem version and the scroll notification
+payload format; no index mapping or query DSL changes are required.
+
+In order to upgrade Chewy 8/Elasticsearch 8 to Chewy 9/Elasticsearch 9 in the most seamless manner you have to:
+
+* Upgrade to the latest 8.x stable releases (Chewy 8.0.1, Elasticsearch 8.19.x). Your ES cluster must be on 8.19.x before upgrading to 9.x.
+* Study carefully [Breaking changes in 9.0](https://www.elastic.co/docs/release-notes/elasticsearch/breaking-changes), make sure your application conforms. Notable changes that may affect Chewy users:
+  * Stricter bulk API request parsing — malformed action lines that were previously tolerated are now rejected.
+  * The legacy `_knn_search` endpoint has been removed — use the `knn` clause in `_search` instead.
+  * Date histogram aggregations on boolean fields are no longer supported.
+  * Elasticsearch now returns HTTP 429 (instead of 5xx) for certain timeout conditions — update any retry logic that keys on 5xx status codes.
+* Update the `elasticsearch` gem — Chewy 9 requires `elasticsearch >= 8.14`.
+  * **Important:** The `elasticsearch` Ruby gem at version 9.x sends a `compatible-with=9` HTTP header that Elasticsearch 8.x servers reject with HTTP 400. Keep the gem pinned to `~> 8.14` (i.e. gem version 8.x) until after your Elasticsearch cluster has been upgraded to 9.x. You may optionally upgrade the gem to version 9.x after the cluster upgrade is complete.
+* Update scroll notification subscribers:
+  * The `search_query.chewy` notification payload for scroll requests now nests `scroll_id` under `body:`:
+    * Old format: `{scroll: '1m', scroll_id: '...'}`
+    * New format: `{scroll: '1m', body: {scroll_id: '...'}}`
+  * Update any application code that subscribes to scroll notification payloads:
+
+    ```ruby
+    # Before (Chewy < 9)
+    ActiveSupport::Notifications.subscribe('search_query.chewy') do |*, payload|
+      scroll_id = payload[:request][:scroll_id]
+    end
+
+    # After (Chewy 9+)
+    ActiveSupport::Notifications.subscribe('search_query.chewy') do |*, payload|
+      scroll_id = payload[:request].dig(:body, :scroll_id)
+    end
+    ```
+
+* Run your test suite on Chewy 9 / Elasticsearch 9.
+* Run manual tests on Chewy 9 / Elasticsearch 9.
+* Deploy Chewy 9 (with the `elasticsearch` gem still pinned to `~> 8.14`).
+* Perform a [rolling upgrade](https://www.elastic.co/docs/deploy-manage/upgrade/deployment-or-cluster) of Elasticsearch to 9.x.
+* (Optional) Remove the `elasticsearch` gem version pin, allowing the gem to resolve to 9.x.
+
 ## Chewy 7/Elasticsearch 7 to Chewy 8/Elasticsearch 8
 
 In order to upgrade Chewy 7/Elasticsearch 7 to Chewy 8/Elasticsearch 8 in the most seamless manner you have to:
diff --git a/spec/chewy/runtime_spec.rb b/spec/chewy/runtime_spec.rb
index e8cc457d..782d01ba 100644
--- a/spec/chewy/runtime_spec.rb
+++ b/spec/chewy/runtime_spec.rb
@@ -4,6 +4,6 @@
   describe '.version' do
     specify { expect(described_class.version).to be_a(described_class::Version) }
     specify { expect(described_class.version).to be >= '8.0' }
-    specify { expect(described_class.version).to be < '9.0' }
+    specify { expect(described_class.version).to be < '10.0' }
   end
 end
diff --git a/spec/chewy/search/scrolling_spec.rb b/spec/chewy/search/scrolling_spec.rb
index ec9cefb7..bd4eac29 100644
--- a/spec/chewy/search/scrolling_spec.rb
+++ b/spec/chewy/search/scrolling_spec.rb
@@ -84,7 +84,11 @@
       end
 
       context do
-        before { expect(Chewy.client).to receive(:scroll).twice.and_call_original }
+        before do
+          expect(Chewy.client).to receive(:scroll)
+            .with(hash_including(scroll: '1m', body: hash_including(:scroll_id)))
+            .twice.and_call_original
+        end
         specify do
           expect(request.scroll_batches(batch_size: 2).map do |batch|
             batch.map { |hit| hit['_source']['rating'] }
@@ -181,7 +185,7 @@
             hash_including(
               index: [CitiesIndex, CountriesIndex],
               indexes: [CitiesIndex, CountriesIndex],
-              request: {scroll: '1m', scroll_id: an_instance_of(String)}
+              request: {scroll: '1m', body: {scroll_id: an_instance_of(String)}}
             )
           ])
         end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index ac8d86f6..f87fa190 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -49,11 +49,12 @@
 # )
 
 # Low-level substitute for now-obsolete drop_indices.
-# Uses format: 'json' for version-portable parsing.
+# Uses format: 'json' for version-portable parsing and `.body` to unwrap
+# the Elasticsearch::API::Response (required for ES 9.x gem).
 # System indices (prefixed with '.') are excluded to avoid deleting
 # ES-internal indices like .security or .kibana.
 def drop_indices
-  indices = Chewy.client.cat.indices(format: 'json')
+  indices = Chewy.client.cat.indices(format: 'json').body
     .map { |entry| entry['index'] }
     .reject { |name| name.start_with?('.') }
   return if indices.blank?