An orthosis for the correction of a varus/valgus malalignment of a person comprises a support device which in the frontal plane has an L shape and a support limb reaching under the foot of the person and establishing contact with a tread and a splint arrangement extending laterally upwards along the leg, said splint arrangement being connectible to the lower leg of the person via a fastening device. The splint arrangement is subdivided into a contact limb to rest laterally against the foot and a splint to rest laterally against the lower leg and to exert a torque onto the lower leg by a rotary joint which is arranged approximately at the level of the ankle joint. The orthosis allows an effective correction of the malalignment using only one foot part and a splint which extends laterally along the lower leg.