ALSA a small river of Venetia (Plin. Nat. 3.18. s.22) still called the Ausa, which flows into the lagunes of Marano, a few miles W. of Aquileia. A battle was fought on its banks in A.D. 340, between the younger Constantine and the generals of his brother Constans, in which Constantine himself was slain, and his body thrown into the river Alsa. (Victor, Epit. 41.21; Hieron. Chron. ad ann. 2356.)