In the most famous version of the legend, as described by Virgile in Aeneid, a Trojan priest Laocoön when the Greeks, who were holding Troy under siege, left the Trojan Horse on the coast had warned his fellow citizens against the Greeks "even if they bear gifts". The Greek goddess Athena, acting as protector of the Greeks, punished Laocoön for his interference by having him and his two sons attacked by the giant sea serpents Porces and Chariboea.

According to the legend told by Homer in the Iliad, Laocoön, the son of Priam and the priest of Apollo, advised the Trojans not to bring a wooden horse into the city. He said: "I am afraid of the Danes even when they bring gifts." Laocoön thus provoked the wrath of the goddess Athena, the protector of the Achaeans, and she sent two giant serpents to drown him and his sons.

According to another legend, Laocoön incurs the wrath of Apollo on himself and his sons by breaking the priestly law by marrying and having sons, and by daring to kiss his wife in the sanctuary in front of the statue of Apollo in a sacred temple. Because of that Apollo sent two sea serpents on him and his sons, which will take them forever into the darkness of the chthonic world after a dramatic fight.