The trapezium bone (greater multangular bone) is a carpal bone in the wrist. It forms the radial border of the carpal tunnel. The trapezium is distinguished by a deep groove on its anterior surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone (the metacarpal bone of the thumb). It is homologous with the first distal carpal of reptiles and amphibians.