Februarius, fully Mensis Februarius, was the shortest month of the Roman calendar from which the Julian and Gregorian month of February derived. It was eventually placed second in order, preceded by Ianuarius and followed by Martius. In the oldest Roman calendar, which the Romans believed to have been instituted by their legendary founder Romulus, March was the first month, and the calendar year had only ten months in all. Ianuarius and Februarius were supposed to have been added by Numa Pompilius, the second king of Rome, originally at the end of the year. It is unclear when the Romans reset the course of the year so that January and February came first.

Lupercalia, also known as Lupercal, was a pastoral festival of Ancient Rome observed annually on February 15 to purify the city, promoting health and fertility. Lupercalia was also known as dies Februatus, after the purification instruments called februa, the basis for the month named Februarius.