diff --git a/types/transducers.js/index.d.ts b/types/transducers.js/index.d.ts
new file mode 100644
index 0000000000..504496c1fb
--- /dev/null
+++ b/types/transducers.js/index.d.ts
@@ -0,0 +1,213 @@
+// Type definitions for transducers.js 0.3
+// Project: https://github.com/jlongster/transducers.js
+// Definitions by: David Philipson <https://github.com/dphilipson>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+
+export type Reducer<TResult, TInput> = (
+    result: TResult,
+    input: TInput,
+) => TResult;
+
+export type Transducer<TInput, TOutput> = <TResult>(
+    xf: Transformer<TResult, TOutput>,
+) => Transformer<TResult, TInput>;
+
+export interface CompletingTransformer<TResult, TCompleteResult, TInput> {
+    ["@@transducer/init"](): TResult | void;
+    ["@@transducer/result"](result: TResult): TCompleteResult;
+    ["@@transducer/step"](
+        result: TResult,
+        input: TInput,
+    ): TResult | Reduced<TResult>;
+}
+
+export type Transformer<TResult, TInput> = CompletingTransformer<
+    TResult,
+    TResult,
+    TInput
+>;
+
+export interface Reduced<T> {
+    ["@@transducer/reduced"]: true;
+    ["@@transducer/value"]: T;
+}
+
+export function reduce<TResult, TInput>(
+    coll: Iterable<TInput>,
+    xf: Transformer<TResult, TInput>,
+    init: TResult,
+): TResult;
+export function reduce<TResult, TCompleteResult, TInput>(
+    coll: Iterable<TInput>,
+    xf: CompletingTransformer<TResult, TCompleteResult, TInput>,
+    init: TResult,
+): TCompleteResult;
+// Overloads for object iteration.
+export function reduce<TResult, TInput>(
+    coll: { [key: string]: TInput },
+    xf: Transformer<TResult, [string, TInput]>,
+    init: TResult,
+): TResult;
+export function reduce<TResult, TCompleteResult, TInput>(
+    coll: { [key: string]: TInput },
+    xf: CompletingTransformer<TResult, TCompleteResult, [string, TInput]>,
+    init: TResult,
+): TCompleteResult;
+
+export function transformer<TResult, TInput>(
+    reducer: Reducer<TResult, TInput>,
+): Transformer<TResult, TInput>;
+
+export interface ReducedConstructor {
+    new <T>(value: T): Reduced<T>;
+}
+
+export const Reduced: ReducedConstructor;
+
+export function isReduced(x: any): boolean;
+
+export function iterator<T>(coll: Iterable<T>): IterableIterator<T>;
+
+export function push<T>(arr: T[], x: T): T[];
+
+export function transduce<TResult, TInput, TOutput>(
+    coll: Iterable<TInput>,
+    xf: Transducer<TInput, TOutput>,
+    f: Reducer<TResult, TOutput>,
+    init: TResult,
+): TResult;
+export function transduce<TResult, TCompleteResult, TInput, TOutput>(
+    coll: Iterable<TInput>,
+    xf: Transducer<TInput, TOutput>,
+    f: CompletingTransformer<TResult, TCompleteResult, TOutput>,
+    init?: TResult,
+): TCompleteResult;
+// Overloads for object iteration.
+export function transduce<TResult, TInput, TOutput>(
+    coll: { [key: string]: TInput },
+    xf: Transducer<[string, TInput], TOutput>,
+    f: Reducer<TResult, TOutput>,
+    init: TResult,
+): TResult;
+export function transduce<TResult, TCompleteResult, TInput, TOutput>(
+    coll: { [key: string]: TInput },
+    xf: Transducer<[string, TInput], TOutput>,
+    f: CompletingTransformer<TResult, TCompleteResult, TOutput>,
+    init?: TResult,
+): TCompleteResult;
+
+export function seq<TInput, TOutput>(
+    coll: TInput[],
+    xf: Transducer<TInput, TOutput>,
+): TOutput[];
+export function seq<TInput, TOutput>(
+    coll: Iterable<TInput>,
+    xf: Transducer<TInput, TOutput>,
+): IterableIterator<TOutput>;
+export function seq<TInput, TOutput>(
+    coll: { [key: string]: TInput },
+    xf: Transducer<[string, TInput], [string, TOutput]>,
+): { [key: string]: TOutput };
+
+export function toArray<TInput, TOutput>(
+    coll: Iterable<TInput>,
+    xf?: Transducer<TInput, TOutput>,
+): TOutput[];
+export function toArray<TInput, TOutput>(
+    coll: { [key: string]: TInput },
+    xf?: Transducer<[string, TInput], TOutput>,
+): TOutput[];
+
+export function toIter<TInput, TOutput>(
+    coll: Iterable<TInput>,
+    xf?: Transducer<TInput, TOutput>,
+): IterableIterator<TOutput>;
+export function toIter<TInput, TOutput>(
+    coll: { [key: string]: TInput },
+    xf?: Transducer<[string, TInput], TOutput>,
+): IterableIterator<TOutput>;
+
+export function toObj<TInput, TOutput>(
+    coll: Iterable<TInput>,
+    xf?: Transducer<TInput, [string, TOutput]>,
+): { [key: string]: TOutput };
+export function toObj<TInput, TOutput>(
+    coll: { [key: string]: TInput },
+    xf: Transducer<[string, TInput], [string, TOutput]>,
+): { [key: string]: TOutput };
+
+export function into<TInput, TOutput>(
+    to: TOutput[],
+    xf: Transducer<TInput, TOutput>,
+    from: Iterable<TInput>,
+): TOutput[];
+export function into<TInput>(
+    to: string,
+    xf: Transducer<TInput, string>,
+    from: Iterable<TInput>,
+): string;
+export function into<TInput, TOutput>(
+    to: { [key: string]: TOutput },
+    xf: Transducer<TInput, [string, TOutput]>,
+    from: Iterable<TInput>,
+): { [key: string]: TOutput };
+
+export function compose(...fs: Array<(x: any) => any>): (x: any) => any;
+
+export function map<TInput, TOutput>(
+    f: (x: TInput) => TOutput,
+): Transducer<TInput, TOutput>;
+
+export function filter<TInput>(
+    pred: (x: TInput) => boolean,
+): Transducer<TInput, TInput>;
+
+export function remove<TInput>(
+    pred: (x: TInput) => boolean,
+): Transducer<TInput, TInput>;
+
+export function cat<TResult, TInput>(
+    f: Transformer<TResult, TInput>,
+): Transformer<TResult, Iterable<TInput>>;
+
+export function mapcat<TInput, TOutput>(
+    f: (x: TInput) => Iterable<TOutput>,
+): Transducer<TInput, TOutput>;
+
+export function keep<TInput>(): Transducer<TInput | null | undefined, TInput>;
+
+export function dedupe<TInput>(): Transducer<TInput, TInput>;
+
+export function take<TInput>(n: number): Transducer<TInput, TInput>;
+
+export function takeWhile<TInput>(
+    pred: (x: TInput) => boolean,
+): Transducer<TInput, TInput>;
+
+export function takeNth<TInput>(n: number): Transducer<TInput, TInput>;
+
+export function drop<TInput>(n: number): Transducer<TInput, TInput>;
+
+export function dropWhile<TInput>(
+    pred: (x: TInput) => boolean,
+): Transducer<TInput, TInput>;
+
+export function partition<TInput>(n: number): Transducer<TInput, TInput[]>;
+
+export function partitionBy<TInput>(
+    f: (x: TInput) => any,
+): Transducer<TInput, TInput[]>;
+
+export function interpose<TInput>(sep: TInput): Transducer<TInput, TInput>;
+
+export function repeat<TInput>(n: number): Transducer<TInput, TInput>;
+
+export function range(n: number): number[];
+
+export interface LazyTransformerConstructor {
+    new <TInput, TOutput>(xf: Transducer<TInput, TOutput>, coll: Iterable<
+        TInput
+    >): IterableIterator<TOutput>;
+}
+
+export const LazyTransformer: LazyTransformerConstructor;
diff --git a/types/transducers.js/transducers.js-tests.ts b/types/transducers.js/transducers.js-tests.ts
new file mode 100644
index 0000000000..e7a64d1432
--- /dev/null
+++ b/types/transducers.js/transducers.js-tests.ts
@@ -0,0 +1,37 @@
+import * as t from "transducers.js";
+
+const stringAppendFn: t.Reducer<string, number> = (acc, x) => acc + x;
+const stringAppendTransformer = t.transformer(stringAppendFn);
+const stringAppendThenLengthTransformer: t.CompletingTransformer<
+    string,
+    number,
+    number
+> = {
+    ["@@transducer/init"]: () => "",
+    ["@@transducer/result"]: (s: string) => s.length,
+    ["@@transducer/step"]: stringAppendFn,
+};
+const toNumberTransducer: t.Transducer<string, number> = t.map(s => +s);
+const transducedString1: string = t.transduce(
+    ["1", "2"],
+    toNumberTransducer,
+    stringAppendFn,
+    "",
+);
+const transducedString2: string = t.transduce(
+    ["1", "2"],
+    toNumberTransducer,
+    stringAppendTransformer,
+);
+
+const mapcatted: number[] = t.into([], t.mapcat((s: string) => [1, 2, 3, 4]), [
+    "a",
+    "b",
+]);
+
+const partitionedIter: Iterator<number[]> = t.toIter(
+    [1, 2, 3, 4, 5],
+    t.partition<number>(2),
+);
+
+const reduced: t.Reduced<string> = new t.Reduced("a");
diff --git a/types/transducers.js/tsconfig.json b/types/transducers.js/tsconfig.json
new file mode 100644
index 0000000000..9d2e6f5b96
--- /dev/null
+++ b/types/transducers.js/tsconfig.json
@@ -0,0 +1,22 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true
+    },
+    "files": [
+        "index.d.ts",
+        "transducers.js-tests.ts"
+    ]
+}
diff --git a/types/transducers.js/tslint.json b/types/transducers.js/tslint.json
new file mode 100644
index 0000000000..d88586e5bd
--- /dev/null
+++ b/types/transducers.js/tslint.json
@@ -0,0 +1,3 @@
+{
+  "extends": "dtslint/dt.json"
+}