A lighting device for vehicles comprising: - a housing configured to be mounted on board a vehicle and in turn comprising a base body delimiting an inner cavity and provided with at least one upper opening for access to said inner cavity and a cover that is able to be overlappingly coupled to the base body for closing the at least one upper opening; - at least one light source housed in said inner cavity together with any attachments thereof; and - a power supply system for the at least one light source and any attachments thereof, comprising an electric circuit housed in said inner cavity, a first connector electrically and mechanically connected to said electric circuit by means of a flexible connection element, and a second connector connected to a supply cable, the first connector being configured to be mounted on the outside of the base body and to receive said second connector in electrical and mechanical coupling; characterized in that i) the first connector is carried integral by a plate element and projects from a first face of the plate element, the plate element being mechanically integral with said flexible connection element; ii) a lateral wall of the base body, arranged adjacent to said at least one upper access opening of the base body, carries externally to the base body a couple of guides configured to be slidingly engaged by respective opposite lateral edges of the plate element; iii) the cover carries externally overhanging, at a portion of said lateral wall arranged between said guides, a protrusion open towards the base body and internally delimiting a reception seat configured to receive the first and the second connectors (13,15) with the cover coupled to the base body only when the first and the second connector (13,15) are electrically and mechanically coupled to each other correctly. - a housing configured to be mounted on board a vehicle and in turn comprising a base body delimiting an inner cavity and provided with at least one upper opening for access to said inner cavity and a cover that is able to be overlappingly coupled to the base body for closing the at least one upper opening; - at least one light source housed in said inner cavity together with any attachments thereof; and - a power supply system for the at least one light source and any attachments thereof, comprising an electric circuit housed in said inner cavity, a first connector electrically and mechanically connected to said electric circuit by means of a flexible connection element, and a second connector connected to a supply cable, the first connector being configured to be mounted on the outside of the base body and to receive said second connector in electrical and mechanical coupling; characterized in that i) the first connector is carried integral by a plate element and projects from a first face of the plate element, the plate element being mechanically integral with said flexible connection element; ii) a lateral wall of the base body, arranged adjacent to said at least one upper access opening of the base body, carries externally to the base body a couple of guides configured to be slidingly engaged by respective opposite lateral edges of the plate element; iii) the cover carries externally overhanging, at a portion of said lateral wall arranged between said guides, a protrusion open towards the base body and internally delimiting a reception seat configured to receive the first and the second connectors (13,15) with the cover coupled to the base body only when the first and the second connector (13,15) are electrically and mechanically coupled to each other correctly. i) the first connector is carried integral by a plate element and projects from a first face of the plate element, the plate element being mechanically integral with said flexible connection element; ii) a lateral wall of the base body, arranged adjacent to said at least one upper access opening of the base body, carries externally to the base body a couple of guides configured to be slidingly engaged by respective opposite lateral edges of the plate element; iii) the cover carries externally overhanging, at a portion of said lateral wall arranged between said guides, a protrusion open towards the base body and internally delimiting a reception seat configured to receive the first and the second connectors (13,15) with the cover coupled to the base body only when the first and the second connector (13,15) are electrically and mechanically coupled to each other correctly.