The National Roman Museum and Baths of Diocletian was a public bathhouse in ancient Rome and is located on Viminal Hill.

Construction on the baths began in 298 AD and was completed in 306 AD, the building was commissioned by emperor Maximian, named after Diocletian and completed by Constanius.

The building took up 120,000 square metres and included a gymnasium, a library, and cold, hot and tepid public baths.

In 2008 the baths became a part of the National Museum of Rome and can be visited by the public.