Janus was the two-faced Roman god who presided over beginnings, doors, and transitions.
Janus governed passages from one state or place to another: entrances and exits, beginnings and endings, journeys, exchanges, and changes in status. His double-faced image symbolized the ability to look backward and forward at once. This made him an especially fitting deity for thresholds and new starts.
Romans invoked Janus at the beginning of religious ceremonies, even when another god was the principal focus. The month of January, Ianuarius in Latin, takes its name from him. His associations extended beyond household doors to city gates, roads, boundaries, and the opening or closing of military activity.
The Temple of Janus in Rome was traditionally opened during war and closed during peace, although periods of closure were rare. He should not be confused with Terminus, who guarded boundaries, or Saturn, associated with agriculture and the Golden Age. Faunus was linked with nature, prophecy, and the countryside, not primarily transitions.