Tosa is a city located in Kōchi Prefecture, Japan. As of 1 August 2022, the city had an estimated population of 26,427 in 12,671 households and a population density of 290 persons per km2. The total area of the city is 91.50 square kilometres (35.33 sq mi). The city of Tosa should not be confused with the historical Tosa Province, which covered all of modern-day Kōchi Prefecture.

Kōchi Prefecture is a prefecture of Japan located on the island of Shikoku. Kōchi Prefecture has a population of 669,516 and has a geographic area of 7,103 km2. Kōchi Prefecture borders Ehime Prefecture to the northwest and Tokushima Prefecture to the northeast.