The invention concerns a hand orthosis for supporting the thumb, the orthosis comprising a main part (1) comprising: a first portion (2) in the form of a sleeve fitted to a portion of the thumb extending to the fold area between the thumb and the palm of the hand, a second portion (4) assembled by a seam line in the form of a sleeve fitted to the wrist, a third portion (3) linking the first and second portions, shaped so as to envelop an area of the hand extending along the thumb metacarpal between the back of the hand and the palm, and comprising an opening to allow the palm of the hand to pass therethrough, the main part being shaped so as not to cover the fold area between the thumb and the palm of the hand and being made from an elastic material having a Young's modulus of between 0.5Mpa and 1Mpa in a direction corresponding to a longitudinal axis of the first portion.
