A three-dimensional target capable of serving as a positioning reference, including, on a useful face, a first structure and a second structure. The first structure defines a planar reference face divided up between at least a first portion whose surface is reflective according to a diffuse reflection, and a second portion whose surface is reflective according to a specular reflection, the second portion being divided up according to a series of localized zones positioned in the first portion. The second structure has an inclined face relative to the planar reference face. Applicable to three-dimensional optical measurement of the relative position between a first object and a second object.