In Greek mythology, Patroclus, or Pátroklos (gr. Πάτροκλος "glory of the father") was Achilles' best friend and possibly lover, son of Menoetius. In the Iliad, the relationship between Patroclus and Achilles is a an important part of the story that contributes to the overall theme of the humanization of Achilles after his public humiliation by Agamemnon early in the book. While the Iliad does not explicitly say so, in later Greek writings, such as Plato's Symposium, the relationship between Patroclus and Achilles is held up as a model of homosexual love. This relationship is generally seen as a starting point for literary scholars working within queer theory. However, ancient Greek thinking about gender and sexuality were more concerned with the social status of the sexual partner than whether the sex was of a hetero- or homosexual nature.

In his youth, Patroclus killed a friend of his, Clysonymus, during an argument. His father had to escape into exile with Patroclus to escape punishment, and they took shelter at the palace of King Peleus, Achilleus' father. Peleus sent the boys to live in the wilderness and be raised by Chiron, the wise king of the centaurs.

Homer's Iliad inspired this pottery art of the chariot races at Patroclus's funeral games.

Patroclus fought with the Greeks in the Trojan War and killed Sarpedon(a son of Zeus), Kebriones(the chariot driver of Hector), and many other Trojans. When Achilleus refused to fight because of his feud with Agamemnon, Patroclus donned his armor and was killed by Hector and Euphorbos, with help from Apollo. After retrieving his body, which had been protected on the field by Menelaus and Telamonian Aias, Achilles returned to battle and avenged his friend's death by killing Hector and desecrated his body behind his chariot instead of allowing the Trojans to honorably dispose of it by burning it. Achilleus' grief was huge and for some time refused to bury Patroclus' body, but he was persuaded to do so by an apparition of Patroclus, who told him he could not enter the underworld without a proper cremation. Achilleus cut a lock of his hair and sacrificed horses, dogs, and twelve Trojan captives before placing Patroclus' body on the funeral pyre.

Achilleus then organized an athletic competition to honour his dead friend, which included a chariot race (won by Diomedes), boxing (won by Epeios), wrestling (a draw between Telamonian Aias and Odysseus), a foot race (won by Odysseus), a duel (a draw between Aias and Diomedes), a discus throw (won by Polypoites), an archery contest (won by Meriones), and a javelin throw (won by Agamemnon, unopposed). The games are described in Book 23 of the Iliad, one of the earliest references to Greek sport.