An ambidextrous wrist brace is described, having a substantially rectangular main strap (2) designed to be closed in a tubular shape around the wrist and provided with a slot (21) through which the user's thumb passes to be immobilized by an immobilization system (3) connected to the main strap (2). The thumb immobilization system (3) includes a rod (30) substantially bent into a U-shape to give rise to two end arms (31) which engage telescopically in respective pockets (9, 9') formed on the main strap (2), so as to be able to adjust the thumb immobilizer (3) in position.