Abstract: The invention relates to a rotor (11) for an electrical machine, in particular for a motor vehicle, having an axis of rotation (X), a rotor radius (Rr), a polar step (?), and including a body (31) comprising a plurality of rotor teeth (40) defining cavities (36) in which permanent magnets (37) are accommodated, each rotor tooth (40) comprising a single lip (41) for radial retention of a permanent magnet, and an assembly of magnetic poles (50), each pole having a curvature in the form of an arc of a circle, the said arc of a circle being defined by a radius of curvature (Rc), a centre of curvature (Cc), and a polar angle (2?p), the said rotor having a ratio (r) between the radius of curvature (Rc) and the rotor radius (Rr) contained between 0.52 and 0.63, and a ratio (?) between the polar half-angle (?p) and the polar step (?) contained between 0.62 and 0.80.