The Yonesaka Line is a railway line in Japan, operated by East Japan Railway Company. It connects Yonezawa Station in Yamagata Prefecture to Sakamachi Station in Niigata Prefecture. At Yonezawa, connections to the Yamagata Shinkansen and Ōu Main Line can be made; while the Uetsu Main Line connects at Sakamachi Station. The line takes its name from the first kanji of Yonezawa (米沢) and Sakamachi (坂町).

The Ōu Main Line is a railway line in Japan, operated by the East Japan Railway Company. It connects Fukushima Station through Akita Station to Aomori Station. Since the opening of the Yamagata Shinkansen on July 1, 1992, the Fukushima–Yamagata section is sometimes referred to as the Yamagata Line. The name of the line as a whole refers to the ancient provinces of Mutsu (陸奥) and Dewa (出羽), as it connects both ends of Mutsu by passing north–south through Dewa.