Eupolis was an Athenian comic playwright of the 5th century BCE, a leading figure in the genre known as Old Comedy. He was a contemporary and rival of Aristophanes. Ancient records indicate he was born around 446 BCE and won his first major dramatic competition in 429 BCE. The circumstances of his death are uncertain; a later story claims he was killed at sea by the politician Alcibiades, but many scholars consider this a legend, and he may have died in battle.

He was a prolific author, credited in antiquity with 17 plays, though only fragments of his work survive today. His comedies were known for their bold political and personal satire. Notable lost plays include Demoi ("The Demes"), which brought back famous Athenian statesmen from the past to critique current politics, and Baptai ("The Dippers"), which mocked the controversial figure Alcibiades. Other works, like Kolakes ("The Flatterers"), targeted prominent intellectuals and wealthy patrons in Athenian society.

According to modern scholars, Eupolis was ranked in antiquity as one of the three great masters of Old Comedy, alongside Cratinus and Aristophanes. The fragments of his plays are crucial for understanding the full scope of the genre, revealing a tradition deeply engaged in the political debates and personalities of Athens during the Peloponnesian War. The loss of his complete works represents a significant gap in classical literature.