Diphilus (Greek: Δίφιλος), of Sinope, was a poet of the new Attic comedy and contemporary of Menander (342-291 BC). Most of his plays were written and acted at Athens, but he led a wandering life, and died at Smyrna.

He was on intimate terms with the famous courtesan Gnathaena (Athenaeus xiii. pp. 579, 583). He is said to have written 100 comedies; of these plays, only the titles and associated fragments of fifty-four of them are preserved. He sometimes acted himself. To judge from the imitations of Plautus (Casina from the Κληρούμενοι, Asinaria from the Ὀναγός, Rudens from some other play), he was very skilful in the construction of his plots. Terence also tells us that he introduced into the Adelphi (ii. I) a scene from the Συναποθνήσκοντες, which had been omitted by Plautus in his adaptation (Commorientes) of the same play.