Antonius Diogenes was a Greek author of the Roman Imperial period, likely active in the 2nd century CE. No reliable biographical details about his life survive. His Roman family name Antonius paired with the Greek name Diogenes reflects the culturally blended elite of his era.

His definitive work is the lost prose novel The Wonders Beyond Thule, summarized in the 9th-century Bibliotheca of the patriarch Photius, who noted it spanned 24 books. Two other dubious titles, On the Incredible Things in the Cosmos and On the Incredible Things in Taprobane, are occasionally attributed to him based on a contested entry in the Suda lexicon.

Antonius Diogenes is a significant figure in the history of ancient fiction. The Wonders Beyond Thule was a comprehensive compendium mixing adventure, romance, and the supernatural, which influenced later literature. Its complex narrative framework and vast scope made it a key precursor to the Greek romance genre. It was famously parodied by Lucian in his True History and is considered a possible source for the novelist Longus.