The Spercheios (Greek: Σπερχειός, Sperkheiós), also known as the Spercheus from its Latin name, is a river in Phthiotis in central Greece. It is 80 km (50 mi) long, and its drainage area is 1,830 km2 (710 sq mi). It was worshipped as a god in the ancient Greek religion and appears in some collections of Greek mythology. In antiquity, its upper valley was known as Ainis. In AD 997, its valley was the site of the Battle of Spercheios, which ended Bulgarian incursions into the Byzantine Empire.