Abstract: The ankle joint orthesis for the stabilization of the internal and external ankle joint comprises a medial shell and a lateral shell made of plastic. The shells extend from the heel region beyond the malleolus to the lower calf region. The shells are lined throughout the entire support surface with a flexible padding. Loop and hook type fastening structure are provided for fastening and securing the shells. One shell, preferably the lateral shell, is of an L-shaped design and has a laterally extending leg which extends below the foot between the heel and the ball of the foot. Both shells can be connected to each other by loop and hook type fastening structure under the foot, e.g., a selectively adhesive strap fastened to one of the shells and passing under the foot for being adhesively secured to a mating strap closure on the other shell. Both shells have openings in the malleolar area.