diff --git a/src/Language/AST/NodeKind.php b/src/Language/AST/NodeKind.php
index d321cdc..7c0f300 100644
--- a/src/Language/AST/NodeKind.php
+++ b/src/Language/AST/NodeKind.php
@@ -69,6 +69,9 @@ class NodeKind
 
     const DIRECTIVE_DEFINITION = 'DirectiveDefinition';
 
+    // Type System Extensions
+    const SCHEMA_EXTENSION = 'SchemaExtension';
+
     /** @var string[] */
     public static $classMap = [
         self::NAME                         => NameNode::class,
diff --git a/src/Language/AST/SchemaTypeExtensionNode.php b/src/Language/AST/SchemaTypeExtensionNode.php
new file mode 100644
index 0000000..e86177d
--- /dev/null
+++ b/src/Language/AST/SchemaTypeExtensionNode.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Language\AST;
+
+class SchemaTypeExtensionNode extends Node implements TypeExtensionNode
+{
+    /** @var string */
+    public $kind = NodeKind::SCHEMA_EXTENSION;
+
+    /** @var DirectiveNode[]|null */
+    public $directives;
+
+    /** @var OperationTypeDefinitionNode[]|null */
+    public $operationTypes;
+}
diff --git a/src/Language/Parser.php b/src/Language/Parser.php
index 6f0ce0a..76939a0 100644
--- a/src/Language/Parser.php
+++ b/src/Language/Parser.php
@@ -44,6 +44,7 @@ use GraphQL\Language\AST\OperationTypeDefinitionNode;
 use GraphQL\Language\AST\ScalarTypeDefinitionNode;
 use GraphQL\Language\AST\ScalarTypeExtensionNode;
 use GraphQL\Language\AST\SchemaDefinitionNode;
+use GraphQL\Language\AST\SchemaTypeExtensionNode;
 use GraphQL\Language\AST\SelectionSetNode;
 use GraphQL\Language\AST\StringValueNode;
 use GraphQL\Language\AST\TypeExtensionNode;
@@ -1446,6 +1447,8 @@ class Parser
 
         if ($keywordToken->kind === Token::NAME) {
             switch ($keywordToken->value) {
+                case 'schema':
+                    return $this->parseSchemaTypeExtension();
                 case 'scalar':
                     return $this->parseScalarTypeExtension();
                 case 'type':
@@ -1464,6 +1467,33 @@ class Parser
         throw $this->unexpected($keywordToken);
     }
 
+    /**
+     * @return SchemaTypeExtensionNode
+     * @throws SyntaxError
+     */
+    private function parseSchemaTypeExtension()
+    {
+        $start = $this->lexer->token;
+        $this->expectKeyword('extend');
+        $this->expectKeyword('schema');
+        $directives = $this->parseDirectives(true);
+        $operationTypes = $this->peek(Token::BRACE_L)
+            ? $this->many(
+                Token::BRACE_L,
+                [$this, 'parseOperationTypeDefinition'],
+                Token::BRACE_R
+            ) : [];
+        if (count($directives) === 0 && count($operationTypes) === 0) {
+            $this->unexpected();
+        }
+
+        return new SchemaTypeExtensionNode([
+            'directives' => $directives,
+            'operationTypes' => $operationTypes,
+            'loc' => $this->loc($start)
+        ]);
+    }
+
     /**
      * @return ScalarTypeExtensionNode
      * @throws SyntaxError
diff --git a/src/Language/Printer.php b/src/Language/Printer.php
index f5110f1..7c3bbb4 100644
--- a/src/Language/Printer.php
+++ b/src/Language/Printer.php
@@ -41,6 +41,7 @@ use GraphQL\Language\AST\OperationTypeDefinitionNode;
 use GraphQL\Language\AST\ScalarTypeDefinitionNode;
 use GraphQL\Language\AST\ScalarTypeExtensionNode;
 use GraphQL\Language\AST\SchemaDefinitionNode;
+use GraphQL\Language\AST\SchemaTypeExtensionNode;
 use GraphQL\Language\AST\SelectionSetNode;
 use GraphQL\Language\AST\StringValueNode;
 use GraphQL\Language\AST\UnionTypeDefinitionNode;
@@ -335,6 +336,17 @@ class Printer
                         );
                     }),
 
+                    NodeKind::SCHEMA_EXTENSION => function (SchemaTypeExtensionNode $def) {
+                        return $this->join(
+                            [
+                                'extend schema',
+                                $this->join($def->directives, ' '),
+                                $this->block($def->operationTypes)
+                            ],
+                            ' '
+                        );
+                    },
+
                     NodeKind::SCALAR_TYPE_EXTENSION => function (ScalarTypeExtensionNode $def) {
                         return $this->join(
                             [
diff --git a/src/Language/Visitor.php b/src/Language/Visitor.php
index 94c83e7..6487913 100644
--- a/src/Language/Visitor.php
+++ b/src/Language/Visitor.php
@@ -165,6 +165,8 @@ class Visitor
         NodeKind::INPUT_OBJECT_TYPE_EXTENSION => ['name', 'directives', 'fields'],
 
         NodeKind::DIRECTIVE_DEFINITION => ['description', 'name', 'arguments', 'locations'],
+
+        NodeKind::SCHEMA_EXTENSION => ['directives', 'operationTypes']
     ];
 
     /**
diff --git a/src/Type/Schema.php b/src/Type/Schema.php
index 4d86298..a3f3294 100644
--- a/src/Type/Schema.php
+++ b/src/Type/Schema.php
@@ -8,6 +8,7 @@ use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
 use GraphQL\GraphQL;
 use GraphQL\Language\AST\SchemaDefinitionNode;
+use GraphQL\Language\AST\SchemaTypeExtensionNode;
 use GraphQL\Type\Definition\AbstractType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\InterfaceType;
@@ -67,6 +68,9 @@ class Schema
     /** @var InvariantViolation[]|null */
     private $validationErrors;
 
+    /** @var SchemaTypeExtensionNode[] */
+    public $extensionASTNodes;
+
     /**
      * @api
      * @param mixed[]|SchemaConfig $config
@@ -111,6 +115,8 @@ class Schema
         }
 
         $this->config = $config;
+        $this->extensionASTNodes = $config->extensionASTNodes;
+
         if ($config->query) {
             $this->resolvedTypes[$config->query->name] = $config->query;
         }
diff --git a/src/Type/SchemaConfig.php b/src/Type/SchemaConfig.php
index 3be1c98..142bafd 100644
--- a/src/Type/SchemaConfig.php
+++ b/src/Type/SchemaConfig.php
@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace GraphQL\Type;
 
 use GraphQL\Language\AST\SchemaDefinitionNode;
+use GraphQL\Language\AST\SchemaTypeExtensionNode;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
@@ -51,6 +52,9 @@ class SchemaConfig
     /** @var bool */
     public $assumeValid;
 
+    /** @var SchemaTypeExtensionNode[] */
+    public $extensionASTNodes;
+
     /**
      * Converts an array of options to instance of SchemaConfig
      * (or just returns empty config when array is not passed).
@@ -100,6 +104,10 @@ class SchemaConfig
             if (isset($options['assumeValid'])) {
                 $config->setAssumeValid((bool) $options['assumeValid']);
             }
+
+            if (isset($options['extensionASTNodes'])) {
+                $config->setExtensionASTNodes($options['extensionASTNodes']);
+            }
         }
 
         return $config;
@@ -266,4 +274,20 @@ class SchemaConfig
 
         return $this;
     }
+
+    /**
+     * @return SchemaTypeExtensionNode[]
+     */
+    public function getExtensionASTNodes(): array
+    {
+        return $this->extensionASTNodes;
+    }
+
+    /**
+     * @param SchemaTypeExtensionNode[] $extensionASTNodes
+     */
+    public function setExtensionASTNodes(array $extensionASTNodes): void
+    {
+        $this->extensionASTNodes = $extensionASTNodes;
+    }
 }