The month of January is named after Janus, the Roman god linked with beginnings and transitions.
Janus was associated with doorways, gates, passages, and changes from one state to another. Roman tradition often portrayed him with two faces, allowing him to look backward and forward, an image that fits the transition from an old year to a new one.
January was named for Janus because it marks a boundary in the Roman calendar. The Latin name Ianuarius became the source of the month’s name in English and many related languages.
Janus is not the same figure as Saturn, whose festival Saturnalia was celebrated in December, or Mars, who gave his name to March. The modern New Year date of January 1 also reflects later calendar reforms and historical changes rather than one single unbroken Roman practice.