Construcciones y Auxiliar de Ferrocarriles, S.A. is a Spanish multinational company headquartered in Beasain, Gipuzkoa, specializing in the design, manufacture, and supply of comprehensive railway solutions. Founded in 1917 as Compañía Auxiliar de Ferrocarriles, it has evolved into a global leader in rolling stock, producing high-speed trains, metro units, trams, regional and commuter trains, locomotives, and buses through its subsidiary Solaris Bus & Coach. The company offers end-to-end services including system design, civil works, electrification, signaling, maintenance, and turnkey projects under concession models. With over 17,000 employees and operations in more than 60 countries, Construcciones y Auxiliar de Ferrocarriles maintains production facilities in Spain, France, the UK, Poland, the US, Mexico, and Brazil. Its portfolio features innovative platforms like Oaris high-speed trains, Civity regional trains, and Urbos trams, serving urban transit, high-speed networks, and multimodal mobility. Notable projects include the Kaohsiung Tramway in Taiwan, Mexico's Suburban Railway, and extensions to metro lines worldwide, emphasizing sustainable transport solutions that integrate advanced technologies for safety, efficiency, and environmental respect.