The invention concerns a luminaire having a housing, which at the emission side of the luminaire has a housing opening, having, situated in the housing, connection means for at least one lamp which define the position thereof in the housing, having a light guiding element which is so positioned that, in the main emission direction, it is located in front of the lamp to be used, and having at least one diffuser arranged at the side neighbouring the light guiding element, which has a shaping projecting beyond the edge of the housing, having a flank rising towards the light guiding element. In order to improve the light guiding and/or light emission of the diffuser, the shaping has further a flank falling towards the light guiding element.