An embodiment of a magnetic-field sensor includes a magnetic-field sensor arrangement and a magnetic body which has, for example, an inhomogeneous magnetization. The magnetic body has a recess facing the magnetic-field sensor arrangement and resulting in a non-convex cross-sectional area, the magnetic body is annular or comprises an annular section, and the magnetic body is fixedly arranged with respect to the magnetic-field sensor arrangement and forms a back-bias magnet for the magnetic-field sensor arrangement.