Which Roman god is the month of January named after?

January is named after Janus, the Roman god associated with beginnings, transitions and doorways.

Janus was commonly depicted with two faces, one looking forward and one looking backward. That image made the god an apt namesake for the first month of the Roman and modern Gregorian year: January looks toward the year that has ended and the year that is beginning. The month is called Ianuarius in Latin.

Roman religious tradition connected Janus with gates, passages and changes of state. Unlike many Roman gods, Janus was not usually represented as having a Greek equivalent. His symbolism made him especially relevant to ceremonies marking openings, departures and new starts.

January was not always the first month in Rome's earliest calendar traditions. Roman calendar reforms eventually established January 1 as the beginning of the civil year, although different communities and institutions historically used different dates. Modern New Year's customs inherit the month name even when their celebrations are secular.