The invention relates to a motor vehicle suspension arm (4) including two shell halves (14, 16) attached to one another along a median joining plane (L) and forming the structure of the arm (4); the two shell halves (14, 16) include first attachment edges (18, 20) extending in the median joining plane (L) and in mutual contact in said plane, and second attachment edges (22, 24) extending transversely, preferably perpendicularly, to said plane (L), said second attachment edges being in mutual contact in the transverse area thereof. The invention also relates to a motor vehicle including such a suspension arm (4), the arm being hingedly mounted to the structure of the vehicle and to a wheel of said vehicle.