Minamibōsō is a city located in Chiba Prefecture, Japan. As of 1 November 2020, the city had an estimated population of 37,143 in 17,175 households and a population density of 160 persons per km². The total area of the city is 230.22 square kilometres (88.89 sq mi), making it the fifth largest city in Chiba Prefecture in terms of area.

The Bōsō Peninsula is a peninsula that encompasses the entirety of Chiba Prefecture on Honshu, the largest island of Japan. It is part of the Greater Tokyo Area. It forms the eastern edge of Tokyo Bay, separating it from the Pacific Ocean. The peninsula covers approximately 5,034 square kilometres (1,944 sq mi).