Janus is the Roman god whose name gives January its name and who is symbolically associated with the start of the New Year.
Janus was associated with beginnings, transitions, doorways, gates, and passages. Roman artistic representations commonly show him with two faces, one looking forward and one looking backward. That imagery made him an especially fitting symbol for the boundary between the old year and the new.
The month of January is named for Janus. In the Roman calendar, January 1 became the beginning of the consular year in 153 BCE, although calendar practices changed over Roman history. The modern New Year date ultimately reflects later calendar developments as well as Roman influence.
Janus is not the same figure as Saturn, whose festival Saturnalia was held in December. Nor is January named after a Roman emperor. The connection is linguistic and religious: the month’s name derives from the Latin name Ianus.