An exalted Roman god, a figure of great antiquity and obscure origin. Always represented as having two faces, one looking forwards, the other backwards, Janus presided over the past, present, and future, over gates, doorways, entrances, and beginnings, which the Romans believed ensured good endings.

His principal temple in the Forum had doors facing east and west for the beginning and ending of the day.

Janus was publicly invoked on the first day of January, the month named for him.

Janus also presided over war and peace. At every sacrifice, in every prayer, he was the first god invoked, taking precedence before Jupiter. When war was declared, the portals to the sanctuary of Janus on the Forum were opened. The portals were again closed on the declaration of peace. During the entire history of Rome, this happened on a handful of occasions only.

As the most ancient of kings, Janus is supposed to have given the exiled Kronos a warm welcome in Italy, and to have offered Kronos a share of the royal duties.