Diophantus ( Dióphantos), son of Asclepiodorus, of Sinope, was a general in the service of Mithridates VI of Pontus. Diophantus was active in Mithridates' campaigns in the Bosporan Kingdom and elsewhere around the Black Sea, although their chronology is disputed. An inscription found during the excavations in Chersonesos glorifies Diophantus as "the first foreign invader to conquer the Scythians".
During his first Crimean expedition, he relieved the siege of Chersonesos by the Scythian king Palacus and subdued his allies, the Tauri. He finished this campaign at Scythian Neapolis.