Janus, the ancient Roman god commonly shown with two faces, gave January its name.
Janus was associated with doors, gates, beginnings, transitions, and passages. His two faces were traditionally interpreted as looking in opposite directions, symbolizing attention to what has passed and what is beginning. That imagery fits New Year’s celebrations especially well, because the occasion connects reflection on the old year with hopes for the new one.
The Roman month Januarius was named for Janus. Under the Julian calendar, January became the first month of the year, reinforcing the god’s connection with beginnings. January 1 was established as the start of the Roman civil year in 153 BCE, when Roman consuls began taking office on that date.
Janus is not the same figure as Saturn, whose festival Saturnalia was held in December. Nor is the two-faced image simply a symbol of dishonesty in its original Roman context. In classical religion, it primarily expressed dual viewpoints, thresholds, and the movement from one state to another.