Janus, the Roman god of beginnings and transitions, gives January its name and is honored by the month's New Year association.
The Roman month Ianuarius was named for Janus, whose two faces traditionally look in opposite directions. This imagery suited a god connected with doorways, transitions, endings, and beginnings. As January opens a new year while leaving the old one behind, Janus became a natural symbol for the month.
The Roman calendar did not always begin in January. January became the first month of the Roman consular year in 153 BCE, and the Julian calendar later helped establish the arrangement that influenced the modern Gregorian calendar. Janus is therefore connected to New Year symbolism, but he is not the name of a Roman New Year's Eve festival.