The invention pertains to a rotor blade for a wind power system as well as a wind power system. The present invention is based on the objective of disclosing a rotor blade with a rotor blade profile and a corresponding wind power system that make it possible to improve the efficiency in comparison with arrangements known thus far. In the proposed rotor blade for a wind power system, the position of maximum thickness of the rotor blade lies approximately between 15% and 40%, preferably between 23% and 28%, and the maximum profile thickness lies approximately between 20% and 45%, preferably between 32% and 36%.