The invention finds application in the field of electric valve actuators. Particularly, the invention relates to a magnetic absolute angular position sensor for valves controlled by electric part-turn actuators, wherein the rotation of the valve shaft (10) induces a change in the direction along which the lines of the magnetic field generated by a magnet (8) integral therewith, pass through a stationary circuit board (7), containing two Wheatstone bridges arranged at 45 to each other, and made of a magneto-resistive material. Hence, two 90 electric signals X and Y are generated, having the same amplitude, which allow to uniquely determine the angle of rotation of the shaft (10).