In Greek mythology, Thersites, son of Agrius, was a rank-and-file soldier of the Greek army during the Trojan War.

Homer described him in detail in the Iliad. He is said to be bow-legged, lame and had shoulders that caved inward. His head was covered in tufts of hair and came to a point. He was vulgar and obscene. He called Agamemnon greedy and Achilles a coward, causing Odysseus to hit him with Agamemnon's sceptre.

According to later stories, Achilles eventually killed him for making fun of Achilles' grief over the death of Penthesilea.

Along with many of the major figures of the Trojan War, Thersites was also a character in Shakespeare's Troilus and Cressida. He begins as Ajax' slave, telling Ajax, "I would thou didst itch from head to foot and I had the scratching of thee; I would make thee the loathsomest scab in Greece." Thersites soon leaves Ajax and puts himself into the service of Achilles (portrayed by Shakespeare as kind of bohemian figure), who appreciates his bitter, caustic humor.