Abstract: A blade of a rotor for a rotary wing aircraft. The blade presents a combination of relationships for variation in the sweep, the chord, and the twist of the airfoil profiles of the sections of the blade in order, firstly to improve the aerodynamic performance of the blade both in forward flight and in stationary flight, and secondly to reduce the noise given off during approach flight. The blade is double-tapered and presents three sweeps. The twist relationship is substantially constant over a first portion of the blade, and then decreases over the remainder of the blade in linear or in non-linear manner. Suitable variation in the gradient of the twist of the blade makes it possible to improve the aerodynamic performance of the blade in forward flight and in hovering flight.