Dosan Line is a railway line in Shikoku, Japan, operated by the Shikoku Railway Company. It connects Tadotsu Station in Tadotsu, Kagawa, and Kubokawa Station in Shimanto, Kōchi. The line links the city of Kōchi with northern Shikoku and the island of Honshū via the Seto-Ōhashi Line. The first section of the line between Tadotsu and Kotohira opened in 1889, Kochi was connected to the northern section of the line in 1935, and the western extension of the line was completed in 1951. The name of the line comes from "Tosa" (土佐) and "Sanuki" (讃岐), the old provincial names of present-day Kōchi Prefecture and Kagawa Prefecture, respectively.

Kōchi is the capital city of Kōchi Prefecture located on the island of Shikoku in Japan. With over 40% of the prefectural population, Kōchi is the main commercial and industrial centre and the "primate city" of the prefecture. As of 1 April 2023, the city had an estimated population of 318,520 in 154,048 households, and a population density of 1,000 persons per km2. The total area of the city is 309.00 square kilometres (119.31 sq mi).