Which Saturn moon shares its orbit with Epimetheus?

Which Saturn moon shares its orbit with Epimetheus? Janus does. The two moons occupy nearly identical paths around Saturn and are the Solar System’s only known pair of co-orbital moons of comparable size.

Their gravity prevents a collision by making them exchange orbital positions. Roughly every four years, the inner moon gains energy and moves outward while the outer moon moves inward. They pass one another at a safe distance of about 10,000 kilometres rather than merging or colliding.

Janus was first identified in 1966, but observations were confusing because Epimetheus was initially mistaken for the same object. The two-body explanation became clear in 1978 and was confirmed by Voyager 1 in 1980. A common mix-up is to call Epimetheus the sole answer: it is also co-orbital with Janus, but the question asks which moon shares Epimetheus’s orbit, making Janus the canonical response.