diff --git a/src/GraphQL/DirectiveProviderExtensionInterface.php b/src/GraphQL/DirectiveProviderExtensionInterface.php
new file mode 100644
index 000000000..759111408
--- /dev/null
+++ b/src/GraphQL/DirectiveProviderExtensionInterface.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Drupal\graphql\GraphQL;
+
+/**
+ * Interface for Schema extensions that provide new directives.
+ *
+ * @package Drupal\graphql\GraphQL
+ */
+interface DirectiveProviderExtensionInterface {
+
+  /**
+   * Retrieve all directive definitions as a string.
+   *
+   * @return string
+   *   Directive definitions in SDL.
+   */
+  public function getDirectiveDefinitions() : string;
+
+}
diff --git a/src/GraphQL/ParentAwareSchemaExtensionInterface.php b/src/GraphQL/ParentAwareSchemaExtensionInterface.php
new file mode 100644
index 000000000..ff973ebde
--- /dev/null
+++ b/src/GraphQL/ParentAwareSchemaExtensionInterface.php
@@ -0,0 +1,22 @@
+<?php
+
+namespace Drupal\graphql\GraphQL;
+
+use GraphQL\Language\AST\DocumentNode;
+
+/**
+ * Interface for schema extensions that need to inspect the host schema.
+ *
+ * @package Drupal\graphql\GraphQL
+ */
+interface ParentAwareSchemaExtensionInterface {
+
+  /**
+   * Pass the parent schema document to the extension.
+   *
+   * @param \GraphQL\Language\AST\DocumentNode $document
+   *   The parent schema document.
+   */
+  public function setParentSchemaDocument(DocumentNode $document): void;
+
+}
diff --git a/src/Plugin/GraphQL/Schema/ComposableSchema.php b/src/Plugin/GraphQL/Schema/ComposableSchema.php
index eeb439e47..3ff2062a5 100644
--- a/src/Plugin/GraphQL/Schema/ComposableSchema.php
+++ b/src/Plugin/GraphQL/Schema/ComposableSchema.php
@@ -6,6 +6,8 @@
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Plugin\PluginFormInterface;
+use Drupal\graphql\GraphQL\DirectiveProviderExtensionInterface;
+use Drupal\graphql\GraphQL\ParentAwareSchemaExtensionInterface;
 use Drupal\graphql\GraphQL\ResolverRegistry;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 
@@ -29,23 +31,58 @@ public function getResolverRegistry() {
    * {@inheritdoc}
    */
   protected function getExtensions() {
-    return array_map(function ($id) {
+    $extensions = array_map(function ($id) {
       return $this->extensionManager->createInstance($id);
     }, array_filter($this->getConfiguration()['extensions']));
+
+    $schemaDocument = $this->getSchemaDocument($extensions);
+    // Iterate through all extensions and pass them the current schema, so they
+    // can act on it.
+    foreach ($extensions as $extension) {
+      if ($extension instanceof ParentAwareSchemaExtensionInterface) {
+        $extension->setParentSchemaDocument($schemaDocument);
+      }
+    }
+
+    return $extensions;
   }
 
   /**
    * {@inheritdoc}
    */
   protected function getSchemaDefinition() {
-    return <<<GQL
-      type Schema {
-        query: Query
+    $extensions = parent::getExtensions();
+
+    // Get all extensions and prepend any defined directives to the schema.
+    $schema = [];
+    foreach ($extensions as $extension) {
+      if ($extension instanceof DirectiveProviderExtensionInterface) {
+        $schema[] = $extension->getDirectiveDefinitions();
       }
+    }
 
-      type Query
+    // Attempt to load a schema file and return it instead of the hardcoded
+    // empty schema.
+    $id = $this->getPluginId();
+    $definition = $this->getPluginDefinition();
+    $module = $this->moduleHandler->getModule($definition['provider']);
+    $path = 'graphql/' . $id . '.graphqls';
+    $file = $module->getPath() . '/' . $path;
+
+    if (!file_exists($file)) {
+      $schema[] = <<<GQL
+        type Schema {
+          query: Query
+        }
+
+        type Query
 GQL;
+    }
+    else {
+      $schema[] = file_get_contents($file);
+    }
 
+    return implode("\n", $schema);
   }
 
   /**
diff --git a/tests/modules/graphql_extension_directives_test/graphql/extension_directives_test.base.graphqls b/tests/modules/graphql_extension_directives_test/graphql/extension_directives_test.base.graphqls
new file mode 100644
index 000000000..05d2c7415
--- /dev/null
+++ b/tests/modules/graphql_extension_directives_test/graphql/extension_directives_test.base.graphqls
@@ -0,0 +1,4 @@
+type Car @dimensions(includeDepth: true) {
+  brand: String!
+  model: String!
+}
diff --git a/tests/modules/graphql_extension_directives_test/graphql/extension_directives_test.extension.graphqls b/tests/modules/graphql_extension_directives_test/graphql/extension_directives_test.extension.graphqls
new file mode 100644
index 000000000..3f949dfb7
--- /dev/null
+++ b/tests/modules/graphql_extension_directives_test/graphql/extension_directives_test.extension.graphqls
@@ -0,0 +1,3 @@
+extend type Query {
+  cars: [Car]
+}
diff --git a/tests/modules/graphql_extension_directives_test/graphql_extension_directives_test.info.yml b/tests/modules/graphql_extension_directives_test/graphql_extension_directives_test.info.yml
new file mode 100644
index 000000000..ba028b8d1
--- /dev/null
+++ b/tests/modules/graphql_extension_directives_test/graphql_extension_directives_test.info.yml
@@ -0,0 +1,7 @@
+name: Graphql Extension Directives Test
+type: module
+description: 'Test module for directives provided by extensions.'
+package: Testing
+core_version_requirement: ^8 || ^9
+dependencies:
+  - graphql:graphql
diff --git a/tests/modules/graphql_extension_directives_test/src/Plugin/GraphQL/SchemaExtension/ExtensionDirectivesTestSchemaExtension.php b/tests/modules/graphql_extension_directives_test/src/Plugin/GraphQL/SchemaExtension/ExtensionDirectivesTestSchemaExtension.php
new file mode 100644
index 000000000..9166bf70d
--- /dev/null
+++ b/tests/modules/graphql_extension_directives_test/src/Plugin/GraphQL/SchemaExtension/ExtensionDirectivesTestSchemaExtension.php
@@ -0,0 +1,135 @@
+<?php
+
+namespace Drupal\graphql_extension_directives_test\Plugin\GraphQL\SchemaExtension;
+
+use Drupal\graphql\GraphQL\DirectiveProviderExtensionInterface;
+use Drupal\graphql\GraphQL\ParentAwareSchemaExtensionInterface;
+use Drupal\graphql\GraphQL\ResolverBuilder;
+use Drupal\graphql\GraphQL\ResolverRegistryInterface;
+use Drupal\graphql\Plugin\GraphQL\SchemaExtension\SdlSchemaExtensionPluginBase;
+use GraphQL\Language\AST\ObjectTypeDefinitionNode;
+
+/**
+ * Schema extension plugin.
+ *
+ * @SchemaExtension(
+ *   id = "extension_directives_test",
+ *   name = "Extension Directives Test",
+ *   description = "Provides resolvers for testing extension directives.",
+ *   schema = "composable"
+ * )
+ */
+class ExtensionDirectivesTestSchemaExtension extends SdlSchemaExtensionPluginBase implements ParentAwareSchemaExtensionInterface, DirectiveProviderExtensionInterface {
+
+  /**
+   * The parent schema's AST.
+   *
+   * @var \GraphQL\Language\AST\DocumentNode
+   */
+  protected $parentAst;
+
+  /**
+   * Stores found types with the dimensions directive.
+   *
+   * @var array
+   */
+  protected $typesWithDimensions = [];
+
+  /**
+   * {@inheritDoc}
+   */
+  public function setParentSchemaDocument($document): void {
+    $this->parentAst = $document;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getDirectiveDefinitions(): string {
+    return <<<GQL
+      directive @dimensions(
+        includeDepth: Boolean!
+      ) on OBJECT
+GQL;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function getExtensionDefinition() {
+    $schema = [];
+    $typesWithDimensions = $this->getTypesWithDimensions();
+
+    foreach ($typesWithDimensions as $typeWithDimensions) {
+      $schema[] = "extend type $typeWithDimensions[type_name] {";
+      $schema[] = "  width: String!";
+      $schema[] = "  height: String!";
+      if (isset($typeWithDimensions['args']['includeDepth']) && $typeWithDimensions['args']['includeDepth']) {
+        $schema[] = "  depth: String!";
+      }
+      $schema[] = "}";
+    }
+
+    array_unshift($schema, parent::getExtensionDefinition());
+    return implode("\n", $schema);
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  public function registerResolvers(ResolverRegistryInterface $registry): void {
+    $builder = new ResolverBuilder();
+    $registry->addFieldResolver('Query', 'cars', $builder->callback(function () {
+      return [(object) ['brand' => 'Brand', 'model' => 'Model']];
+    }));
+    foreach ($this->getTypesWithDimensions() as $typeWithDimensions) {
+      $registry->addFieldResolver($typeWithDimensions['type_name'], 'width', $builder->callback(function () {
+        return '1';
+      }));
+      $registry->addFieldResolver($typeWithDimensions['type_name'], 'height', $builder->callback(function () {
+        return '1';
+      }));
+      if (isset($typeWithDimensions['args']['includeDepth']) && $typeWithDimensions['args']['includeDepth']) {
+        $registry->addFieldResolver($typeWithDimensions['type_name'], 'depth', $builder->callback(function () {
+          return '1';
+        }));
+      }
+    }
+  }
+
+  /**
+   * Retrieve all directive calls in the host schema.
+   *
+   * @throws \Drupal\Component\Plugin\Exception\PluginException
+   */
+  public function getTypesWithDimensions(): array {
+    if (count($this->typesWithDimensions) === 0) {
+      // Search for object type definitions ...
+      foreach ($this->parentAst->definitions->getIterator() as $definition) {
+        // ... that have directives.
+        if ($definition instanceof ObjectTypeDefinitionNode) {
+          foreach ($definition->directives->getIterator() as $directive) {
+            /** @var \GraphQL\Language\AST\DirectiveNode $directive */
+            $directiveName = $directive->name->value;
+            if ($directiveName != 'dimensions') {
+              continue;
+            }
+            $typeName = $definition->name->value;
+            $args = [];
+            foreach ($directive->arguments->getIterator() as $arg) {
+              /** @var \GraphQL\Language\AST\ArgumentNode $arg */
+              $args[$arg->name->value] = $arg->value->value;
+            }
+            $this->typesWithDimensions[] = [
+              'directive_name' => $directiveName,
+              'type_name' => $typeName,
+              'args' => $args,
+            ];
+          }
+        }
+      }
+    }
+    return $this->typesWithDimensions;
+  }
+
+}
diff --git a/tests/src/Kernel/ExtensionDirectivesTest.php b/tests/src/Kernel/ExtensionDirectivesTest.php
new file mode 100644
index 000000000..672047786
--- /dev/null
+++ b/tests/src/Kernel/ExtensionDirectivesTest.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace Drupal\Tests\graphql\Kernel;
+
+/**
+ * Test the entity_definition data producer and friends.
+ *
+ * @group graphql
+ */
+class ExtensionDirectivesTest extends GraphQLTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $strictConfigSchema = FALSE;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'graphql_extension_directives_test',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp(): void {
+    parent::setUp();
+
+    $this->createTestServer(
+      'composable',
+      '/extension-directives-test',
+      [
+        'schema_configuration' => [
+          'composable' => [
+            'extensions' => [
+              'extension_directives_test' => 'extension_directives_test',
+            ],
+          ],
+        ],
+      ]
+    );
+  }
+
+  /**
+   * Tests that retrieving an entity definition works.
+   */
+  public function testFields(): void {
+    $query = <<<GQL
+      query {
+        cars {
+          brand
+          model
+          width
+          height
+          depth
+        }
+      }
+GQL;
+
+    $this->assertResults($query, [],
+      [
+        'cars' =>
+          [
+            [
+              'brand' => 'Brand',
+              'model' => 'Model',
+              'width' => '1',
+              'height' => '1',
+              'depth' => '1',
+            ],
+          ],
+      ]
+    );
+  }
+
+}