The invention relates to a reflector (1) which comprises an ellipsoidal light reflective wall (21) and a light output (3) lying in a light output plane (32). The light reflective wall is defined as a portion of the internal surface of an ellipsoid. The focal axis (25) of the ellipsoid has a determined angle CC with respect to an axis (V) perpendicular to the light output plane (32). The light reflective wall (21) is the portion of the ellipsoid, which is taken between the most remote point (24) of the ellipsoid from the light output plane and the light output plane (32). The invention further relates to a luminaire which comprises such a reflector and a light source.