The extensor digitorum (or extensor digitorum muscle, latin: musculus extensor digitorum) is a superficial, long muscle of the forearm that belongs to the posterior muscle group, lying in the first or superficial layer.
The extensor digitorum originates from the lateral epicondyle of the humerus.
The extensor digitorum descends vertically and reaches the dorsal surface of the hand where it splits into four tendons. The tendons of the extensor digitorum insert at the bases of the intermediate and distal phalanges of the second to fifth fingers.
The main function of the extensor digitorum is extension of the four digits and extension of the hand.
The extensor digitorum is innervated by the radial nerve.