diff --git a/src/validation/rules/defaults.rs b/src/validation/rules/defaults.rs
index d26bc2e..647a273 100644
--- a/src/validation/rules/defaults.rs
+++ b/src/validation/rules/defaults.rs
@@ -7,7 +7,7 @@ use super::{
     OverlappingFieldsCanBeMerged, PossibleFragmentSpreads, ProvidedRequiredArguments,
     SingleFieldSubscriptions, UniqueArgumentNames, UniqueDirectivesPerLocation,
     UniqueFragmentNames, UniqueOperationNames, UniqueVariableNames, ValuesOfCorrectType,
-    VariablesAreInputTypes, VariablesInAllowedPosition,
+    VariablesAreInputTypes, VariablesInAllowedPosition, KnownOperationTypes
 };
 
 pub fn default_rules_validation_plan() -> ValidationPlan {
@@ -37,6 +37,8 @@ pub fn default_rules_validation_plan() -> ValidationPlan {
     plan.add_rule(Box::new(VariablesInAllowedPosition::new()));
     plan.add_rule(Box::new(ValuesOfCorrectType::new()));
     plan.add_rule(Box::new(UniqueDirectivesPerLocation::new()));
+    plan.add_rule(Box::new(UniqueDirectivesPerLocation::new()));
+    plan.add_rule(Box::new(KnownOperationTypes::new()));
 
     plan
 }
diff --git a/src/validation/rules/known_operation_types.rs b/src/validation/rules/known_operation_types.rs
new file mode 100644
index 0000000..abcc41f
--- /dev/null
+++ b/src/validation/rules/known_operation_types.rs
@@ -0,0 +1,139 @@
+use super::ValidationRule;
+use crate::ast::{    visit_document, OperationVisitor, OperationVisitorContext, SchemaDocumentExtension,
+    };
+use crate::static_graphql::query::*;
+use crate::validation::utils::{ValidationError, ValidationErrorContext};
+
+/// Known operation types
+///
+/// A GraphQL operation is only valid if the operation type is within the schema.
+///
+/// See https://github.com/graphql/graphql-spec/pull/947
+pub struct KnownOperationTypes;
+
+impl KnownOperationTypes {
+    pub fn new() -> Self {
+        KnownOperationTypes
+    }
+}
+
+fn build_error_message(operation_type: &str) -> String {
+  format!("The {} operation is not supported by the schema.", operation_type)
+}
+
+impl<'a> OperationVisitor<'a, ValidationErrorContext> for KnownOperationTypes {
+    fn enter_operation_definition(
+        &mut self,
+        visitor_context: &mut OperationVisitorContext,
+        user_context: &mut ValidationErrorContext,
+        operation_definition: &OperationDefinition,
+    ) {
+        match operation_definition {
+            OperationDefinition::Mutation(mutation) => {
+                if let None = visitor_context.schema.mutation_type() {
+                    user_context.report_error(ValidationError {
+                        locations: vec![mutation.position],
+                        message: build_error_message("mutation"),
+                    });
+                }
+            },
+            OperationDefinition::Subscription(subscription) => {
+                if let None = visitor_context.schema.subscription_type() {
+                    user_context.report_error(ValidationError {
+                        locations: vec![subscription.position],
+                        message: build_error_message("subscription"),
+                    });
+                }
+            },
+            _ => {}
+        }
+    }
+}
+
+impl ValidationRule for KnownOperationTypes {
+    fn validate<'a>(
+        &self,
+        ctx: &'a mut OperationVisitorContext,
+        error_collector: &mut ValidationErrorContext,
+    ) {
+        visit_document(
+            &mut KnownOperationTypes::new(),
+            &ctx.operation,
+            ctx,
+            error_collector,
+        );
+    }
+}
+
+#[test]
+fn one_known_operation() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(KnownOperationTypes {}));
+    let errors = test_operation_with_schema(
+        "{ field }",
+        TEST_SCHEMA,
+        &mut plan,
+    );
+
+    assert_eq!(get_messages(&errors).len(), 0);
+}
+
+#[test]
+fn unknown_mutation_operation() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(KnownOperationTypes {}));
+    let errors = test_operation_with_schema(
+        "mutation { field }",
+        "type Query { _: String }",
+        &mut plan,
+    );
+
+    let messages = get_messages(&errors);
+    assert_eq!(messages.len(), 1);
+    assert_eq!(
+        messages,
+        vec!["The mutation operation is not supported by the schema."]
+    );
+}
+
+#[test]
+fn unknown_subscription_operation() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(KnownOperationTypes {}));
+    let errors = test_operation_with_schema(
+        "subscription { field }",
+        "type Query { _: String }",
+        &mut plan,
+    );
+
+    let messages = get_messages(&errors);
+    assert_eq!(messages.len(), 1);
+    assert_eq!(
+        messages,
+        vec!["The subscription operation is not supported by the schema."]
+    );
+}
+
+#[test]
+fn mixture_of_known_and_unknown_operations() {
+    use crate::validation::test_utils::*;
+
+    let mut plan = create_plan_from_rule(Box::new(KnownOperationTypes {}));
+    let errors = test_operation_with_schema(
+        "query { field }
+        mutation { field }
+        subscription { field }",
+        "type Query { field: String }",
+        &mut plan,
+    );
+
+    let messages = get_messages(&errors);
+    assert_eq!(messages.len(), 2);
+    assert_eq!(
+        messages,
+        vec!["The mutation operation is not supported by the schema.", "The subscription operation is not supported by the schema."]
+    );
+}
diff --git a/src/validation/rules/mod.rs b/src/validation/rules/mod.rs
index 44446e1..c722119 100644
--- a/src/validation/rules/mod.rs
+++ b/src/validation/rules/mod.rs
@@ -25,6 +25,7 @@ pub mod unique_variable_names;
 pub mod values_of_correct_type;
 pub mod variables_are_input_types;
 pub mod variables_in_allowed_position;
+pub mod known_operation_types;
 
 pub use self::defaults::*;
 pub use self::rule::*;
@@ -53,3 +54,4 @@ pub use self::unique_variable_names::*;
 pub use self::values_of_correct_type::*;
 pub use self::variables_are_input_types::*;
 pub use self::variables_in_allowed_position::*;
+pub use self::known_operation_types::*;