diff --git a/underscore-ko/underscore-ko.d.ts b/underscore-ko/underscore-ko.d.ts
new file mode 100644
index 000000000..c10b49d43
--- /dev/null
+++ b/underscore-ko/underscore-ko.d.ts
@@ -0,0 +1,101 @@
+// Type definitions for Underscore-ko 1.2.2 with underscore 1.4
+// Project: https://github.com/kamranayub/UnderscoreKO
+// Definitions by: Maurits Elbers <https://github.com/MagicMau/>
+// Definitions: https://github.com/borisyankov/DefinitelyTyped
+
+/// <reference path="../knockout/knockout.d.ts" />
+/// <reference path="../underscore/underscore.d.ts" />
+
+interface KnockoutObservableArrayFunctions {
+
+    /****
+     Collections
+    *****/
+    each(iterator: ListIterator, context?: any): any[];
+    each(iterator: ObjectIterator, context?: any): any[];
+    forEach(iterator: ObjectIterator, context?: any): any[];
+    forEach(iterator: ListIterator, context?: any): any[];
+
+    map(iterator: ListIterator, context?: any): any[];
+    map(iterator: ObjectIterator, context?: any): any[];
+    collect(iterator: ListIterator, context?: any): any[];
+    collect(iterator: ObjectIterator, context?: any): any[];
+
+    reduce(iterator: any, memo: any, context?: any): any;
+    inject(iterator: any, memo: any, context?: any): any;
+    foldl(iterator: any, memo: any, context?: any): any;
+
+    reduceRight(iterator: any, memo: any, context?: any): any[];
+    foldr(iterator: any, memo: any, context?: any): any[];
+
+    find(iterator: any, context?: any): any;
+    detect(iterator: any, context?: any): any;
+
+    filter(iterator: any, context?: any): any[];
+    select(iterator: any, context?: any): any[];
+
+    where(properties: any): any[];
+
+    reject(iterator: any, context?: any): any[];
+
+    all(iterator: any, context?: any): bool;
+    every(iterator: any, context?: any): bool;
+
+    any(iterator?: any, context?: any): bool;
+    some(iterator?: any, context?: any): bool;
+
+    contains(list: any, value: any): bool;
+    contains(value: any): bool;
+    include(list: any, value: any): bool;
+    include(value: any): bool;
+
+    invoke(methodName: string, arguments: any[]): any;
+    invoke(methodName: string, ...arguments: any[]): any;
+
+    pluck(propertyName: string): string[];
+    max(iterator?: any, context?: any): any;
+    min(iterator?: any, context?: any): any;
+    sortBy(iterator?: any, context?: any): any;
+    groupBy(iterator: any): any;
+    countBy(iterator: any): any;
+    shuffle(): any[];
+    size(): number;
+
+    /****
+     Arrays
+    *****/
+    first(n?: number): any;
+    head(n?: number): any;
+    take(n?: number): any;
+
+    initial(n?: number): any[];
+
+    last(n?: number): any;
+
+    rest(n?: number): any[];
+    tail(n?: number): any[];
+    drop(n?: number): any[];
+
+    compact(): any[];
+    flatten(shallow?: bool): any[];
+    without(...values: any[]): any[];
+    union(...arrays: any[][]): any[];
+    intersection(...arrays: any[][]): any[];
+    difference(...others: any[][]): any[];
+
+    uniq(isSorted?: bool, iterator?: any): any[];
+    unique(isSorted?: bool, iterator?: any): any[];
+
+    zip(...arrays: any[]): any[];
+    object(values?: any[]): any;
+    indexOf(value: any, isSorted?: bool): number;
+    lastIndexOf(value: any, fromIndex?: number): number;
+    sortedIndex(valueL: any, iterator?: any): number;
+    range(stop: number): any[];
+    range(start: number, stop: number, step?: number): any[];
+
+    /****
+     Chaining
+    *****/
+    chain(object: any): UnderscoreWrappedObject;
+}