Athanis of Syracuse was a Syracusan historian of the 4th century BCE. He was a contemporary and associate of the tyrant Dionysius II and, according to Diodorus Siculus, a member of the "Friends" of Dion. Following Dion's assassination in 354 BCE, Athanis was elected a general before being replaced by a democratic faction, placing him directly within Syracuse's turbulent politics.

His sole known work, a History of Sicily, is now lost. It continued the narrative of Philistus of Syracuse from around 363/2 BCE, covering at least the career of Dion from 357 to 354 BCE. The work is cited by Diodorus and listed in the Suda lexicon.

As a participant in the events he described, Athanis provides a valuable primary source for Sicilian history, particularly the downfall of the Dionysian tyranny. His lost history was used by later historians like Diodorus Siculus, bridging a critical gap in the historiographical record of Sicily.