The Sōya line is the northernmost railway of Japan. It's named after the Sōya district at the northern end of the line. The first section of the line opened in 1898 as Teshio line. In 1912 was the line renamed to Sōya line. From Otoineppu, the original Sōya line ran along the eastern coast and reached Wakkanai (present Minami-Wakkanai) in 1922. A new line was built in 1922-1926 between Otoineppu and Wakkanai, which was called Teshio line,different from the former Teshio Line. In 1928 was Sōya line extended to Wakkanai Port (present Wakkanai). When Sakhalin was under Japanese control, Wakkanai was the base for the railway ferries between Japan och Sakhalin. In 1930 was the northern part of Sōya line renamed to Kitami line and the Teshio line was renamed Sōya line. Since then, Sōya line has been running the present way!
The first 9 km north of Asahikawa is electrified, but this is used by freight and depot trains only.

Between Asahikawa and Shin-Asahikawa, the line is also used by Sekihoku line trains.