We provide a detailed and comprehensive anatomic description of the ligaments stabilizing the trapezium and trapeziometacarpal joint. Sixteen ligaments were identified. Fourteen ligaments inserted onto the trapezium and 2 others attached independently to the thumb metacarpal. The ligaments inserting onto the trapezium were the superficial anterior oblique, deep anterior oblique (beak ligament), dorsoradial, posterior oblique, ulnar collateral, dorsal trapezio-trapezoid, volar trapezio-trapezoid, dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, trapezio-third metacarpal, volar scaphotrapezial, radial scaphotrapezial, transverse carpal, and trapezio-capitate ligaments. The remaining 2 ligaments attach onto the thumb metacarpal and are the proper intermetacarpal and the dorsal intermetacarpal. The dorsoradial and deep anterior oblique ligaments play a substantial role in stabilizing the trapeziometacarpal joint, and the deep anterior oblique ligament may function as a pivot for the first metacarpal during palmar abduction to allow rotation (pronation). The dorsal trapezio-second metacarpal, volar trapezio-second metacarpal, and trapezio-third metacarpal ligaments function as tension bands and are required to prevent instability from cantilever bending forces on the trapezium.