Sentō (銭湯^?) is a type of Japanese communal bath house where customers pay for entrance. Traditionally these bath houses have been quite utilitarian, with one large room separating the sexes by a tall barrier, and on both sides, usually a minimum of lined up faucets and a single large bath for the already washed bathers to sit in among others. Since the second half of the 20th century, these communal bath houses have been decreasing in numbers as more and more Japanese residences now have baths. Some Japanese find social importance in going to public baths, out of the theory that physical proximity/intimacy brings emotional intimacy, which is termed skinship in Japanese. Others go to a sentō because they live in a small housing facility without a private bath or to enjoy bathing in a spacious room and to relax in saunas or jet baths that often accompany new or renovated sentōs.

Another type of Japanese public bath is onsen, which uses hot water from a natural hot spring. They are not exclusive: A sentō can be called an onsen if it derives its bath water from naturally heated hot springs. A legal definition exists that can classify a public bathing facility as sentō.