diff --git a/types/core-object/-private/utils.d.ts b/types/core-object/-private/utils.d.ts
new file mode 100644
index 0000000000..35e3880150
--- /dev/null
+++ b/types/core-object/-private/utils.d.ts
@@ -0,0 +1,40 @@
+export type Constructor<Instance> = new (...args: any[]) => Instance;
+export type Mix<T, U> = U & Pick<T, Exclude<keyof T, keyof U>>;
+export type Values<T> = T[keyof T];
+
+/** Just the strings corresponding to method names on the given type */
+export type MethodNames<T> = Values<{ [K in keyof T]: T[K] extends (...args: any[]) => any ? K : never }>;
+
+/**
+ * Given a `this` type, arg types tuple and return type, creates a function-ish
+ * type that can only be only be invoked via `.call` or `.apply`. Because of the
+ * way CoreObject's `_super` works, it's an error to write e.g. `this._super.init()`;
+ */
+export interface CallOrApply<This, Args, Return> {
+    apply: (thisArg: This, args: Args extends undefined ? any[] : Args | IArguments) => Return;
+
+    // TODO support this properly with `...args: Args` once we can restrict to 3.0+ on DT
+    call:
+        Args extends undefined ? (thisArg: This) => Return :
+        Args extends [infer A] ? (thisArg: This, a: A) => Return :
+        Args extends [infer A, infer B] ? (thisArg: This, a: A, b: B) => Return :
+        Args extends [infer A, infer B, infer C] ? (thisArg: This, a: A, b: B, c: C) => Return :
+        Args extends [infer A, infer B, infer C, infer D] ? (thisArg: This, a: A, b: B, c: C, d: D) => Return :
+        (thisArg: This, ...args: any[]) => Return;
+}
+
+/**
+ * The type of `this._super`, which has keys for all methods appearing in the given
+ * type, but forces the caller to use `.call` or `.apply` to invoke them.
+ */
+export type Super<T> = {
+    // TODO just do `infer Args` once we can restrict to 3.0+ on DT
+    [K in MethodNames<T>]:
+        T[K] extends () => infer Return ? CallOrApply<T, undefined, Return> :
+        T[K] extends (a: infer A) => infer Return ? CallOrApply<T, [A], Return> :
+        T[K] extends (a: infer A, b: infer B) => infer Return ? CallOrApply<T, [A, B], Return> :
+        T[K] extends (a: infer A, b: infer B, c: infer C) => infer Return ? CallOrApply<T, [A, B, C], Return> :
+        T[K] extends (a: infer A, b: infer B, c: infer C, d: infer D) => infer Return ? CallOrApply<T, [A, B, C, D], Return> :
+        T[K] extends (...args: any[]) => infer Return ? CallOrApply<T, any[], Return> :
+        never;
+};
diff --git a/types/core-object/core-object-tests.ts b/types/core-object/core-object-tests.ts
new file mode 100644
index 0000000000..b434ee97fc
--- /dev/null
+++ b/types/core-object/core-object-tests.ts
@@ -0,0 +1,163 @@
+import { Mix, MethodNames } from 'core-object/-private/utils';
+import CoreObject, { ExtendOptions, ExtendThisType } from 'core-object';
+
+//////////// Mix ////////////
+
+declare const mix1: Mix<{ a: number }, { b: string }>;
+mix1.a; // $ExpectType number
+mix1.b; // $ExpectType string
+
+declare const mix2: Mix<{ a: number }, { a: string }>;
+mix2.a; // $ExpectType string
+mix2.b; // $ExpectError
+
+//////////// MethodNames ////////////
+
+declare const names1: MethodNames<{ a: string }>;
+names1; // $ExpectType never
+
+declare const names2: MethodNames<{ a: () => number; b(arg: number): void }>;
+names2; // $ExpectType "a" | "b"
+
+declare const names3: MethodNames<{ a: () => 'hi'; b: null }>;
+names3; // $ExpectType "a"
+
+//////////// ExtendOptions ////////////
+
+const extendOptions1: ExtendOptions<{}> = { a: 1, b: 'hi' };
+const extendOptions2: ExtendOptions<{ a: number }> = { b: 'hi' };
+const extendOptions3: ExtendOptions<{ a: number }> = { a: 5 };
+const extendOptions4: ExtendOptions<{ a: number }> = { a: 'hi' }; // $ExpectError
+
+//////////// ExtendThisType ////////////
+
+declare function extendThisType1<T>(options: T & ExtendThisType<{ prop: string; method: () => number }, T>): void;
+extendThisType1({
+    otherMethod() {
+        this.prop; // $ExpectType string
+        this.random; // $ExpectError
+
+        this._super.method.call(this); // $ExpectType number
+        this._super.random; // $ExpectError
+    }
+});
+
+//////////// CoreObject ////////////
+
+const A = CoreObject.extend({
+    foo: 'hello',
+
+    method(): string {
+        return this.foo;
+    }
+});
+
+const a = new A();
+a.foo; // $ExpectType string
+a.bar; // $ExpectError
+a.method(); // $ExpectType string
+
+const B = A.extend({
+    bar: 123,
+
+    other(): string {
+        return this._super.method.call(this) + this.foo;
+    }
+});
+
+const b = new B();
+b.foo; // $ExpectType string
+b.bar; // $ExpectType number
+b.method(); // $ExpectType string
+b.other(); // $ExpectType string
+
+class ClassWithMethods extends CoreObject.extend({
+    extendMethod(arg: number): string {
+        return 'ok';
+    }
+}) {
+    esMethod(arg: string): number {
+        return 123;
+    }
+}
+
+const ExtendSubclass = ClassWithMethods.extend({
+    anotherMethod() {
+        this._super.extendMethod(1); // $ExpectError
+        this._super.esMethod('hi'); // $ExpectError
+
+        this._super.extendMethod.call(this, 1); // $ExpectType string
+        this._super.extendMethod.apply(this, [1]); // $ExpectType string
+
+        this._super.esMethod.call(this, 'hi'); // $ExpectType number
+        this._super.esMethod.apply(this, ['hi']); // $ExpectType number
+    }
+});
+
+class ESSubclass extends ClassWithMethods {
+    anotherMethod() {
+        this._super; // $ExpectError
+
+        super.extendMethod(1); // $ExpectType string
+        super.esMethod('hi'); // $ExpectType number
+    }
+}
+
+ClassWithMethods.extend({ extendMethod: null }); // $ExpectError
+ClassWithMethods.extend({ extendMethod() {} }); // $ExpectError
+ClassWithMethods.extend({ esMethod: null }); // $ExpectError
+ClassWithMethods.extend({ esMethod() {} }); // $ExpectError
+
+ClassWithMethods.extend({
+    extendMethod(arg: number): string {
+        const result = this._super.extendMethod.call(this, arg);
+        result; // $ExpectType string
+        return result;
+    },
+
+    esMethod(arg: string): number {
+        const result = this._super.esMethod.call(this, arg);
+        result; // $ExpectType number
+        return result;
+    }
+});
+
+declare class ClassWithManyMethods extends CoreObject {
+    method0(): 0;
+    method1(a: 'a'): 1;
+    method2(a: 'a', b: 'b'): 2;
+    method3(a: 'a', b: 'b', c: 'c'): 3;
+    method4(a: 'a', b: 'b', c: 'c', d: 'd'): 4;
+    method5(a: 'a', b: 'b', c: 'c', d: 'd', e: 'e'): 5;
+}
+
+ClassWithManyMethods.extend({
+    child(): void {
+        this._super.method0.call(this); // $ExpectType 0
+        this._super.method0.apply(this, []); // $ExpectType 0
+
+        this._super.method1.call(this, 'a'); // $ExpectType 1
+        this._super.method1.apply(this, ['a']); // $ExpectType 1
+        this._super.method1.call(this, 'x'); // $ExpectError
+        this._super.method1.apply(this, ['x']); // $ExpectError
+
+        this._super.method2.call(this, 'a', 'b'); // $ExpectType 2
+        this._super.method2.apply(this, ['a', 'b']); // $ExpectType 2
+        this._super.method2.call(this, 'a', 'x'); // $ExpectError
+        this._super.method2.apply(this, ['a', 'x']); // $ExpectError
+
+        this._super.method3.call(this, 'a', 'b', 'c'); // $ExpectType 3
+        this._super.method3.apply(this, ['a', 'b', 'c']); // $ExpectType 3
+        this._super.method3.call(this, 'a', 'b', 'x'); // $ExpectError
+        this._super.method3.apply(this, ['a', 'b', 'x']); // $ExpectError
+
+        this._super.method4.call(this, 'a', 'b', 'c', 'd'); // $ExpectType 4
+        this._super.method4.apply(this, ['a', 'b', 'c', 'd']); // $ExpectType 4
+        this._super.method4.call(this, 'a', 'b', 'c', 'x'); // $ExpectError
+        this._super.method4.apply(this, ['a', 'b', 'c', 'x']); // $ExpectError
+
+        // Arity 4 is as high as we go for arg checking
+        this._super.method5.call(this, 'foo', 'bar', 'baz'); // $ExpectType 5
+        this._super.method5.apply(this, ['foo', 'bar', 'baz']); // $ExpectType 5
+    }
+});
diff --git a/types/core-object/index.d.ts b/types/core-object/index.d.ts
new file mode 100644
index 0000000000..aa4566cac2
--- /dev/null
+++ b/types/core-object/index.d.ts
@@ -0,0 +1,23 @@
+// Type definitions for core-object 3.0
+// Project: https://github.com/ember-cli/core-object
+// Definitions by: Dan Freeman <https://github.com/dfreeman>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 2.8
+
+import { Mix, Super, Constructor } from './-private/utils';
+
+/** The type of options allowed to be passed to `Base.extend()` */
+export type ExtendOptions<Base> = { [K in keyof Base]?: Base[K] } & Record<string, any>;
+
+/** The `this` type for any methods on the options passed to `Base.extend()` */
+export type ExtendThisType<Base, Ext> = ThisType<Mix<Base, Ext> & { _super: Super<Base> }>;
+
+export default class CoreObject {
+    // TODO restrict to `Record<string, unknown>` once we can restrict to 3.0+ on DT
+    init(options?: Record<string, any>): void;
+
+    static extend<BaseClass extends Constructor<any>, Ext extends ExtendOptions<InstanceType<BaseClass>>>(
+        this: BaseClass,
+        options: Ext & ExtendThisType<InstanceType<BaseClass>, Ext>
+    ): BaseClass & Constructor<Mix<InstanceType<BaseClass>, Ext>>;
+}
diff --git a/types/core-object/tsconfig.json b/types/core-object/tsconfig.json
new file mode 100644
index 0000000000..908527fc38
--- /dev/null
+++ b/types/core-object/tsconfig.json
@@ -0,0 +1,24 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "strictFunctionTypes": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "-private/utils.d.ts",
+        "core-object-tests.ts"
+    ]
+}
diff --git a/types/core-object/tslint.json b/types/core-object/tslint.json
new file mode 100644
index 0000000000..3db14f85ea
--- /dev/null
+++ b/types/core-object/tslint.json
@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }