The present disclosure relates to a lighting system (10) for a motor vehicle trunk, the trunk (12) being delimited by a trunk lid (14) and a body part (16), the trunk lid having a rear end (15), a front end and a width (w) in the lateral direction of the motor vehicle at the rear end, the body part has a trunk lid receiving portion (18) for accommodating the rear end, the lighting system includes a lighting panel (20) located on the underside of the trunk lid, and The trunk lid receiving portion has a first surface (21) facing the lighting panel when the trunk lid is in the closed position, the lighting system is arranged such that light emitted by the lighting panel illuminates the first surface, and the lighting panel extends beyond the trunk At least 50%, preferably at least 70%, and most preferably at least 90% of the width of the cover at its rear end. It also relates to a warning triangle (30) formed by the above detachable lighting panel, a motor vehicle including a lighting system, and an application of the detachable lighting panel for forming a warning triangle.