Yamaguchi, produced in Japan from 1955 to 1965, was a motorcycle manufacturer founded by Yamaguchi Bicycle Company during the rapid expansion of the Japanese motorcycle industry. The brand became known for lightweight two-stroke motorcycles and mopeds, including models such as the YA Series, Pet, and Auto Pet, which were designed to provide affordable transportation for postwar Japan. At its peak, Yamaguchi was one of the country's largest motorcycle producers, exporting machines to international markets and competing with manufacturers such as Honda, Yamaha, and Suzuki. Characterized by simple engineering, reliability, and accessible performance, the company ceased motorcycle production in 1963 during the consolidation of the Japanese motorcycle industry.