diff --git a/src/index.ts b/src/index.ts
index 853a3a2ec0..85ee135fa4 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -366,6 +366,7 @@ export {
   KnownArgumentNamesRule,
   KnownDirectivesRule,
   KnownFragmentNamesRule,
+  KnownOperationTypesRule,
   KnownTypeNamesRule,
   LoneAnonymousOperationRule,
   NoFragmentCyclesRule,
diff --git a/src/validation/__tests__/KnownOperationTypesRules-test.ts b/src/validation/__tests__/KnownOperationTypesRules-test.ts
new file mode 100644
index 0000000000..93ab581725
--- /dev/null
+++ b/src/validation/__tests__/KnownOperationTypesRules-test.ts
@@ -0,0 +1,60 @@
+import { describe, it } from 'mocha';
+
+import { KnownOperationTypesRule } from '../rules/KnownOperationTypesRule.js';
+
+import { expectValidationErrors } from './harness.js';
+
+function expectErrors(queryStr: string) {
+  return expectValidationErrors(KnownOperationTypesRule, queryStr);
+}
+
+function expectValid(queryStr: string) {
+  expectErrors(queryStr).toDeepEqual([]);
+}
+
+describe('Validate: Known operation types', () => {
+  it('one known operation', () => {
+    expectValid(`
+      { field }
+    `);
+  });
+
+  it('unknown mutation operation', () => {
+    expectErrors(`
+      mutation { field }
+    `).toDeepEqual([
+      {
+        message: 'The mutation operation is not supported by the schema.',
+        locations: [{ line: 2, column: 7 }],
+      },
+    ]);
+  });
+
+  it('unknown subscription operation', () => {
+    expectErrors(`
+      subscription { field }
+    `).toDeepEqual([
+      {
+        message: 'The subscription operation is not supported by the schema.',
+        locations: [{ line: 2, column: 7 }],
+      },
+    ]);
+  });
+
+  it('mixture of known and unknown operations', () => {
+    expectErrors(`
+      query { field }
+      mutation { field }
+      subscription { field }
+  `).toDeepEqual([
+      {
+        message: 'The mutation operation is not supported by the schema.',
+        locations: [{ line: 3, column: 7 }],
+      },
+      {
+        message: 'The subscription operation is not supported by the schema.',
+        locations: [{ line: 4, column: 7 }],
+      },
+    ]);
+  });
+});
diff --git a/src/validation/index.ts b/src/validation/index.ts
index dbe8e57dc0..b1998b5300 100644
--- a/src/validation/index.ts
+++ b/src/validation/index.ts
@@ -33,6 +33,9 @@ export { KnownDirectivesRule } from './rules/KnownDirectivesRule.js';
 // Spec Section: "Fragment spread target defined"
 export { KnownFragmentNamesRule } from './rules/KnownFragmentNamesRule.js';
 
+// Spec Section: "Operation Type Existence"
+export { KnownOperationTypesRule } from './rules/KnownOperationTypesRule.js';
+
 // Spec Section: "Fragment Spread Type Existence"
 export { KnownTypeNamesRule } from './rules/KnownTypeNamesRule.js';
 
diff --git a/src/validation/rules/KnownOperationTypesRule.ts b/src/validation/rules/KnownOperationTypesRule.ts
new file mode 100644
index 0000000000..4b17df05fb
--- /dev/null
+++ b/src/validation/rules/KnownOperationTypesRule.ts
@@ -0,0 +1,32 @@
+import { GraphQLError } from '../../error/GraphQLError.js';
+
+import type { ASTVisitor } from '../../language/visitor.js';
+
+import type { ValidationContext } from '../ValidationContext.js';
+
+/**
+ * Known Operation Types
+ *
+ * A GraphQL document is only valid if when it contains an operation,
+ * the root type for the operation exists within the schema.
+ *
+ * See https://spec.graphql.org/draft/#sec-Operation-Type-Existence
+ */
+export function KnownOperationTypesRule(
+  context: ValidationContext,
+): ASTVisitor {
+  const schema = context.getSchema();
+  return {
+    OperationDefinition(node) {
+      const operation = node.operation;
+      if (!schema.getRootType(operation)) {
+        context.reportError(
+          new GraphQLError(
+            `The ${operation} operation is not supported by the schema.`,
+            { nodes: node },
+          ),
+        );
+      }
+    },
+  };
+}
diff --git a/src/validation/specifiedRules.ts b/src/validation/specifiedRules.ts
index 9884bea8b9..fa2d746de4 100644
--- a/src/validation/specifiedRules.ts
+++ b/src/validation/specifiedRules.ts
@@ -19,6 +19,8 @@ import {
 import { KnownDirectivesRule } from './rules/KnownDirectivesRule.js';
 // Spec Section: "Fragment spread target defined"
 import { KnownFragmentNamesRule } from './rules/KnownFragmentNamesRule.js';
+// Spec Section: "Operation Type Existence"
+import { KnownOperationTypesRule } from './rules/KnownOperationTypesRule.js';
 // Spec Section: "Fragment Spread Type Existence"
 import { KnownTypeNamesRule } from './rules/KnownTypeNamesRule.js';
 // Spec Section: "Lone Anonymous Operation"
@@ -91,6 +93,7 @@ export const recommendedRules = Object.freeze([MaxIntrospectionDepthRule]);
  */
 export const specifiedRules: ReadonlyArray<ValidationRule> = Object.freeze([
   ExecutableDefinitionsRule,
+  KnownOperationTypesRule,
   UniqueOperationNamesRule,
   LoneAnonymousOperationRule,
   SingleFieldSubscriptionsRule,