Acheloüs, the longest of all Greek rivers, rising in central Epirus and debouching, after a course of 240 km. (150 mi.; mostly through mountainous gorges), into the NW corner of the Corinthian Gulf. Its lower reaches were affected by heavy alluviation (Hdt. 2. 10. 3; Thuc. 2. 102. 3) and constituted the frequently disputed frontier between Acarnania and Aetolia. Recent geological studies based on coring in the river's delta continue to refine our understanding of this process as it relates to historical periods. Acheloüs was personified early as a water- and river-god (the son of Oceanus and Tethys), from whom all seas, rivers, and springs derived (Hom. Il. 21. 194–7; Hes. Theog. 337–40). For his mythology and widespread depiction in art, see H. P. Isler, LIMC 1/1 (1981) 12–36.