Diphilus was a Greek comic playwright active in the late 4th and early 3rd centuries BCE. He was born in Sinope, a city on the Black Sea, and was a leading figure, alongside Menander and Philemon, in the genre known as New Comedy. This style moved away from the political satire of earlier periods to focus on domestic life, romantic entanglements, and recognizable stock characters. Ancient records indicate he was a prolific author, credited with writing 100 comedies, though he died in Smyrna.

Although none of his plays survive complete, the titles of about 60 are known, such as The Merchant, The Treasure, and Sappho. His work survives only in fragments quoted by later authors. His historical importance stems largely from his influence on Roman comedy. According to modern scholars, the Roman playwrights Plautus and Terence directly adapted several of his Greek originals into Latin. For example, Plautus’s Rudens and Casina are based on plays by Diphilus. Through these Roman adaptations, his plots and characters were preserved, providing valuable insight into the themes and techniques of Hellenistic New Comedy.