The invention proposes an illumination module (10) producing an illumination beam with cutoff, comprising, arranged from back to front along a horizontal optical axis (A—A), an elliptical reflector (12) which delimits a volume of reflection and which has an elliptical surface of reflection (18, 20), at least one light source (14) which is arranged in the vicinity of a first focus (F1) of the reflector (12), and a convergent lens (16) whose focal plane is arranged in the vicinity of the second focus (F2) of the reflector (12), characterized in that the reflector (12) has a horizontal flat surface (22), the upper face (24) of which is reflective, which delimits vertically towards the bottom the volume of reflection, and in that the flat surface (22) of the reflector (12) has a cutoff edge (28) which is arranged in the vicinity of the second focus (F2) of the reflector (12). The invention also proposes a lamp comprising such an illumination module.