The invention relates to a contactless magnetic sensor for detecting a linear or angular position, comprising a moveable ferromagnetic element (1) the position of which is detected, and a stator assembly (2) itself, comprising two ferromagnetic parts (3, 4), defining with the moveable ferromagnetic element (1) two respective air gaps (7, 8), a permanent magnet (5) and a magneto-sensitive element (6) subjected to a magnetic field that depends on the position of the moveable ferromagnetic element (1) and designed to deliver a measurement signal that depends on the magnetic field to which it is subjected. According to the invention, the two ferromagnetic parts (3, 4) define therebetween a third air gap (9), the permanent magnet (5) being rigidly connected only to the first ferromagnetic part (3) and the magneto-sensitive element (6) being placed in the third air gap (9).