Festivals in ancient Rome were a very important part in Roman religious life during both the Republican and Imperial eras, and one of the primary features of the Roman calendar. Feriae were either public (publicae) or private (privatae). State holidays were celebrated by the Roman people and received public funding. Games (ludi), such as the Ludi Apollinares, were not technically feriae, but the days on which they were celebrated were dies festi, holidays in the modern sense of days off work. Although feriae were paid for by the state, ludi were often funded by wealthy individuals. Feriae privatae were holidays celebrated in honor of private individuals or by families. This article deals only with public holidays, including rites celebrated by the state priests of Rome at temples, as well as celebrations by neighborhoods, families, and friends held simultaneously throughout Rome.

The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. Although the term is primarily used for Rome's pre-Julian calendars, it is often used inclusively of the Julian calendar established by the reforms of the Dictator Julius Caesar and Emperor Augustus in the late 1st century BC.