Enipeus Vallis is a valley in the northern hemisphere of the planet Mars. It is centered at lat. 37°N, long. 267°E in the Arcadia quadrangle (MC-3) between the large volcano Alba Mons and the Tempe Terra plateau. The valley follows a gently sinuous, north-south path for a distance of about 357 km (222 mi). It is likely an ancient watercourse that formed during the early Hesperian (or late Noachian) period, around 3.7 billion years ago.