A hand orthosis for supporting the thumb including a main part including: a first portion 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 assembled by a seam line formed as a sleeve fitted to the wrist, a third portion linking the first and second portions, shaped to envelop an area of the hand extending along the thumb metacarpal between the back and the palm of the hand, and including an opening to allow the palm of the hand to pass therethrough, the main part shaped not to cover the fold area between the thumb and the palm of the hand and being made from an elastic material having a Youngs modulus of between 0.5 Mpa and 1 Mpa in a direction corresponding to a longitudinal axis of the first portion.
