A fixing system, comprising: - a lighting device, including an elongated flexible body comprising a casing hosting a light radiation generating structure including a ribbon-shaped substrate whereon there are distributed electrically-powered light radiation sources, wherein the radiation generated by said sources is emitted through at least one light emission surface, wherein the casing is made of a material at least partly light-impermeable and coupling of the portion of the device corresponding to the light radiation emission surface to the casing imparting to the device protection against the penetration of external agents, the body having a pair of longitudinal grooves extending along said elongated body, said grooves having a tapered cross-section with a restricted mouth portion (161, 162) for receiving and retaining in the groove a complementary coupling element (18, 180, 1800), - at least one fixing element including a wire-like body with a pair of mutually opposed elongated ribs, said elongated ribs having a restricted stem portion and an enlarged head portion, said ribs insertable into respective mutually facing longitudinal grooves provided in a pair of said lighting devices adjoining each other with said fixing element interposed therebetween to provide said complementary coupling element (18, 180, 1800), wherein: - said tapered cross-section extends along a substantially circular path with said restricted mouth portion (161, 162) arranged at a chord of said circular path, - said at least one elongated rib (18; 180; 1800) includes material which is more rigid than the material forming the portion of the elongated body of the lighting device hosting said at least one longitudinal groove, said at least one longitudinal groove is formed in said casing in the absence of interference with emission of light radiation from the device through the at least one light emission surface. - a lighting device, including an elongated flexible body comprising a casing hosting a light radiation generating structure including a ribbon-shaped substrate whereon there are distributed electrically-powered light radiation sources, wherein the radiation generated by said sources is emitted through at least one light emission surface, wherein the casing is made of a material at least partly light-impermeable and coupling of the portion of the device corresponding to the light radiation emission surface to the casing imparting to the device protection against the penetration of external agents, the body having a pair of longitudinal grooves extending along said elongated body, said grooves having a tapered cross-section with a restricted mouth portion (161, 162) for receiving and retaining in the groove a complementary coupling element (18, 180, 1800), - at least one fixing element including a wire-like body with a pair of mutually opposed elongated ribs, said elongated ribs having a restricted stem portion and an enlarged head portion, said ribs insertable into respective mutually facing longitudinal grooves provided in a pair of said lighting devices adjoining each other with said fixing element interposed therebetween to provide said complementary coupling element (18, 180, 1800), - said tapered cross-section extends along a substantially circular path with said restricted mouth portion (161, 162) arranged at a chord of said circular path, - said at least one elongated rib (18; 180; 1800) includes material which is more rigid than the material forming the portion of the elongated body of the lighting device hosting said at least one longitudinal groove, said at least one longitudinal groove is formed in said casing in the absence of interference with emission of light radiation from the device through the at least one light emission surface.