Abstract: The invention relates to an orthosis (1) for wearing on a human hand (2) to restrict motion of at least the carpometacarpal joint (CMCj) of the thumb and preferably also of the metacarpophalangeal joint (MCPj) of the thumb (2-1), the orthosis (1) comprising a metacarpus section (3), which, when the orthosis (1) is worn on a hand, extends across the metacarpals of digits 2-5, and a thumb section (4), which section is curved or annular in shape and fits around the thumb (2-1), preferably around the proximal phalanx (6) of the thumb (2-1). The thumb section (4) is connected to the metacarpus section (3) via a thumb metacarpal section (7) that, when the orthosis (1) is worn on a hand (2), extends along and/or around the thumb metacarpal (8).