diff --git a/src/execution/__tests__/mutations-test.js b/src/execution/__tests__/mutations-test.js
index fffe353ff6..8f21b06115 100644
--- a/src/execution/__tests__/mutations-test.js
+++ b/src/execution/__tests__/mutations-test.js
@@ -79,30 +79,30 @@ const schema = new GraphQLSchema({
       immediatelyChangeTheNumber: {
         type: numberHolderType,
         args: { newNumber: { type: GraphQLInt } },
-        resolve: (function (obj, { newNumber }) {
+        resolve(obj, { newNumber }) {
           return obj.immediatelyChangeTheNumber(newNumber);
-        }: any)
+        }
       },
       promiseToChangeTheNumber: {
         type: numberHolderType,
         args: { newNumber: { type: GraphQLInt } },
-        resolve: (function (obj, { newNumber }) {
+        resolve(obj, { newNumber }) {
           return obj.promiseToChangeTheNumber(newNumber);
-        }: any)
+        }
       },
       failToChangeTheNumber: {
         type: numberHolderType,
         args: { newNumber: { type: GraphQLInt } },
-        resolve: (function (obj, { newNumber }) {
+        resolve(obj, { newNumber }) {
           return obj.failToChangeTheNumber(newNumber);
-        }: any)
+        }
       },
       promiseAndFailToChangeTheNumber: {
         type: numberHolderType,
         args: { newNumber: { type: GraphQLInt } },
-        resolve: (function (obj, { newNumber }) {
+        resolve(obj, { newNumber }) {
           return obj.promiseAndFailToChangeTheNumber(newNumber);
-        }: any)
+        }
       }
     },
     name: 'Mutation',
diff --git a/src/execution/execute.js b/src/execution/execute.js
index 612e8d91e8..836747c429 100644
--- a/src/execution/execute.js
+++ b/src/execution/execute.js
@@ -626,13 +626,13 @@ function resolveField(
 
 // Isolates the "ReturnOrAbrupt" behavior to not de-opt the `resolveField`
 // function. Returns the result of resolveFn or the abrupt-return Error object.
-function resolveOrError(
+function resolveOrError<TSource, TContext>(
   exeContext: ExecutionContext,
-  fieldDef: GraphQLField,
+  fieldDef: GraphQLField<TSource, TContext>,
   fieldNode: FieldNode,
-  resolveFn: GraphQLFieldResolver<*>,
-  source: mixed,
-  context: mixed,
+  resolveFn: GraphQLFieldResolver<TSource, TContext>,
+  source: TSource,
+  context: TContext,
   info: GraphQLResolveInfo
 ): Error | mixed {
   try {
@@ -1042,7 +1042,7 @@ function defaultResolveTypeFn(
  * and returns it as the result, or if it's a function, returns the result
  * of calling that function while passing along args and context.
  */
-export const defaultFieldResolver: GraphQLFieldResolver<any> =
+export const defaultFieldResolver: GraphQLFieldResolver<any, *> =
 function (source, args, context, { fieldName }) {
   // ensure source is a value for which property access is acceptable.
   if (typeof source === 'object' || typeof source === 'function') {
@@ -1077,7 +1077,7 @@ function getFieldDef(
   schema: GraphQLSchema,
   parentType: GraphQLObjectType,
   fieldName: string
-): ?GraphQLField {
+): ?GraphQLField<*, *> {
   if (fieldName === SchemaMetaFieldDef.name &&
       schema.getQueryType() === parentType) {
     return SchemaMetaFieldDef;
diff --git a/src/execution/values.js b/src/execution/values.js
index 90d2484312..9c0b340148 100644
--- a/src/execution/values.js
+++ b/src/execution/values.js
@@ -104,7 +104,7 @@ export function getVariableValues(
  * definitions and list of argument AST nodes.
  */
 export function getArgumentValues(
-  def: GraphQLField | GraphQLDirective,
+  def: GraphQLField<*, *> | GraphQLDirective,
   node: FieldNode | DirectiveNode,
   variableValues?: ?{ [key: string]: mixed }
 ): { [key: string]: mixed } {
diff --git a/src/type/definition.js b/src/type/definition.js
index ccd00b0ded..d4365fb3b4 100644
--- a/src/type/definition.js
+++ b/src/type/definition.js
@@ -368,11 +368,11 @@ export class GraphQLObjectType {
   description: ?string;
   isTypeOf: ?GraphQLIsTypeOfFn;
 
-  _typeConfig: GraphQLObjectTypeConfig<*>;
-  _fields: GraphQLFieldMap;
+  _typeConfig: GraphQLObjectTypeConfig<*, *>;
+  _fields: GraphQLFieldMap<*, *>;
   _interfaces: Array<GraphQLInterfaceType>;
 
-  constructor(config: GraphQLObjectTypeConfig<*>) {
+  constructor(config: GraphQLObjectTypeConfig<*, *>) {
     invariant(config.name, 'Type must be named.');
     assertValidName(config.name);
     this.name = config.name;
@@ -387,7 +387,7 @@ export class GraphQLObjectType {
     this._typeConfig = config;
   }
 
-  getFields(): GraphQLFieldMap {
+  getFields(): GraphQLFieldMap<*, *> {
     return this._fields || (this._fields =
       defineFieldMap(this, this._typeConfig.fields)
     );
@@ -436,10 +436,10 @@ function defineInterfaces(
   return interfaces;
 }
 
-function defineFieldMap(
+function defineFieldMap<TSource, TContext>(
   type: GraphQLNamedType,
-  fieldsThunk: Thunk<GraphQLFieldConfigMap<*>>
-): GraphQLFieldMap {
+  fieldsThunk: Thunk<GraphQLFieldConfigMap<TSource, TContext>>
+): GraphQLFieldMap<TSource, TContext> {
   const fieldMap = resolveThunk(fieldsThunk);
   invariant(
     isPlainObj(fieldMap),
@@ -507,10 +507,10 @@ function isPlainObj(obj) {
   return obj && typeof obj === 'object' && !Array.isArray(obj);
 }
 
-export type GraphQLObjectTypeConfig<TSource> = {
+export type GraphQLObjectTypeConfig<TSource, TContext> = {
   name: string;
   interfaces?: Thunk<?Array<GraphQLInterfaceType>>;
-  fields: Thunk<GraphQLFieldConfigMap<TSource>>;
+  fields: Thunk<GraphQLFieldConfigMap<TSource, TContext>>;
   isTypeOf?: ?GraphQLIsTypeOfFn;
   description?: ?string
 };
@@ -527,10 +527,10 @@ export type GraphQLIsTypeOfFn = (
   info: GraphQLResolveInfo
 ) => boolean;
 
-export type GraphQLFieldResolver<TSource> = (
+export type GraphQLFieldResolver<TSource, TContext> = (
   source: TSource,
   args: {[argName: string]: mixed},
-  context: mixed,
+  context: TContext,
   info: GraphQLResolveInfo
 ) => mixed;
 
@@ -549,10 +549,10 @@ export type GraphQLResolveInfo = {
 
 export type ResponsePath = { prev: ResponsePath, key: string | number } | void;
 
-export type GraphQLFieldConfig<TSource> = {
+export type GraphQLFieldConfig<TSource, TContext> = {
   type: GraphQLOutputType;
   args?: GraphQLFieldConfigArgumentMap;
-  resolve?: GraphQLFieldResolver<TSource>;
+  resolve?: GraphQLFieldResolver<TSource, TContext>;
   deprecationReason?: ?string;
   description?: ?string;
 };
@@ -567,16 +567,16 @@ export type GraphQLArgumentConfig = {
   description?: ?string;
 };
 
-export type GraphQLFieldConfigMap<TSource> = {
-  [fieldName: string]: GraphQLFieldConfig<TSource>;
+export type GraphQLFieldConfigMap<TSource, TContext> = {
+  [fieldName: string]: GraphQLFieldConfig<TSource, TContext>;
 };
 
-export type GraphQLField = {
+export type GraphQLField<TSource, TContext> = {
   name: string;
   description: ?string;
   type: GraphQLOutputType;
   args: Array<GraphQLArgument>;
-  resolve?: GraphQLFieldResolver<*>;
+  resolve?: GraphQLFieldResolver<TSource, TContext>;
   isDeprecated?: boolean;
   deprecationReason?: ?string;
 };
@@ -588,8 +588,8 @@ export type GraphQLArgument = {
   description?: ?string;
 };
 
-export type GraphQLFieldMap = {
-  [fieldName: string]: GraphQLField;
+export type GraphQLFieldMap<TSource, TContext> = {
+  [fieldName: string]: GraphQLField<TSource, TContext>;
 };
 
 
@@ -617,10 +617,10 @@ export class GraphQLInterfaceType {
   description: ?string;
   resolveType: ?GraphQLTypeResolver;
 
-  _typeConfig: GraphQLInterfaceTypeConfig;
-  _fields: GraphQLFieldMap;
+  _typeConfig: GraphQLInterfaceTypeConfig<*, *>;
+  _fields: GraphQLFieldMap<*, *>;
 
-  constructor(config: GraphQLInterfaceTypeConfig) {
+  constructor(config: GraphQLInterfaceTypeConfig<*, *>) {
     invariant(config.name, 'Type must be named.');
     assertValidName(config.name);
     this.name = config.name;
@@ -635,7 +635,7 @@ export class GraphQLInterfaceType {
     this._typeConfig = config;
   }
 
-  getFields(): GraphQLFieldMap {
+  getFields(): GraphQLFieldMap<*, *> {
     return this._fields ||
       (this._fields = defineFieldMap(this, this._typeConfig.fields));
   }
@@ -645,9 +645,9 @@ export class GraphQLInterfaceType {
   }
 }
 
-export type GraphQLInterfaceTypeConfig = {
+export type GraphQLInterfaceTypeConfig<TSource, TContext> = {
   name: string,
-  fields: Thunk<GraphQLFieldConfigMap<mixed>>,
+  fields: Thunk<GraphQLFieldConfigMap<TSource, TContext>>,
   /**
    * Optionally provide a custom type resolver function. If one is not provided,
    * the default implementation will call `isTypeOf` on each implementing
diff --git a/src/type/introspection.js b/src/type/introspection.js
index cbd23f15e8..d9a1cd202a 100644
--- a/src/type/introspection.js
+++ b/src/type/introspection.js
@@ -418,7 +418,7 @@ export const __TypeKind = new GraphQLEnumType({
  * so the format for args is different.
  */
 
-export const SchemaMetaFieldDef: GraphQLField = {
+export const SchemaMetaFieldDef: GraphQLField<*, *> = {
   name: '__schema',
   type: new GraphQLNonNull(__Schema),
   description: 'Access the current type schema of this server.',
@@ -426,7 +426,7 @@ export const SchemaMetaFieldDef: GraphQLField = {
   resolve: (source, args, context, { schema }) => schema
 };
 
-export const TypeMetaFieldDef: GraphQLField = {
+export const TypeMetaFieldDef: GraphQLField<*, *> = {
   name: '__type',
   type: __Type,
   description: 'Request the type information of a single type.',
@@ -437,7 +437,7 @@ export const TypeMetaFieldDef: GraphQLField = {
     schema.getType(((name: any): string))
 };
 
-export const TypeNameMetaFieldDef: GraphQLField = {
+export const TypeNameMetaFieldDef: GraphQLField<*, *> = {
   name: '__typename',
   type: new GraphQLNonNull(GraphQLString),
   description: 'The name of the current Object type at runtime.',
diff --git a/src/utilities/TypeInfo.js b/src/utilities/TypeInfo.js
index af4befc06d..298c21825c 100644
--- a/src/utilities/TypeInfo.js
+++ b/src/utilities/TypeInfo.js
@@ -49,7 +49,7 @@ export class TypeInfo {
   _typeStack: Array<?GraphQLOutputType>;
   _parentTypeStack: Array<?GraphQLCompositeType>;
   _inputTypeStack: Array<?GraphQLInputType>;
-  _fieldDefStack: Array<?GraphQLField>;
+  _fieldDefStack: Array<?GraphQLField<*, *>>;
   _directive: ?GraphQLDirective;
   _argument: ?GraphQLArgument;
   _getFieldDef: typeof getFieldDef;
@@ -89,7 +89,7 @@ export class TypeInfo {
     }
   }
 
-  getFieldDef(): ?GraphQLField {
+  getFieldDef(): ?GraphQLField<*, *> {
     if (this._fieldDefStack.length > 0) {
       return this._fieldDefStack[this._fieldDefStack.length - 1];
     }
@@ -226,7 +226,7 @@ function getFieldDef(
   schema: GraphQLSchema,
   parentType: GraphQLType,
   fieldNode: FieldNode
-): ?GraphQLField {
+): ?GraphQLField<*, *> {
   const name = fieldNode.name.value;
   if (name === SchemaMetaFieldDef.name &&
       schema.getQueryType() === parentType) {
diff --git a/src/validation/rules/OverlappingFieldsCanBeMerged.js b/src/validation/rules/OverlappingFieldsCanBeMerged.js
index 89d9e6e4ec..d6ebe56588 100644
--- a/src/validation/rules/OverlappingFieldsCanBeMerged.js
+++ b/src/validation/rules/OverlappingFieldsCanBeMerged.js
@@ -98,7 +98,7 @@ type ConflictReason = [ string, ConflictReasonMessage ];
 // Reason is a string, or a nested list of conflicts.
 type ConflictReasonMessage = string | Array<ConflictReason>;
 // Tuple defining a field node in a context.
-type NodeAndDef = [ GraphQLCompositeType, FieldNode, ?GraphQLField ];
+type NodeAndDef = [ GraphQLCompositeType, FieldNode, ?GraphQLField<*, *> ];
 // Map of array of those.
 type NodeAndDefCollection = { [key: string]: Array<NodeAndDef> };
 
diff --git a/src/validation/validate.js b/src/validation/validate.js
index d85bbbcda7..f97233f0e8 100644
--- a/src/validation/validate.js
+++ b/src/validation/validate.js
@@ -240,7 +240,7 @@ export class ValidationContext {
     return this._typeInfo.getInputType();
   }
 
-  getFieldDef(): ?GraphQLField {
+  getFieldDef(): ?GraphQLField<*, *> {
     return this._typeInfo.getFieldDef();
   }