In Greek mythology, Eurylochus, or Eurýlokhos (Εὐρύλοχος) appears in Homer's Odyssey as second-in-command of Odysseus' ship during the return to Ithaca after the Trojan War. He was also a relative of Odysseus through marriage. He is portrayed as an unpleasant cowardly individual who undermines Odysseus and stirs up trouble.
When the ship stopped on Aeaea, home of Circe the sorcress, Eurylochus and Odysseus draw lots to lead a group of twenty two men to explore the island. Eurylochus is chosen. After the crew spots a column of smoke, Eurylochus leads his expedition towards the source. They soon near a palace surrounded with wild but magically benign animals. Inside the palace is Circe singing, and (led by Polites) all of Eurylochus' party except for himself rush inside to greet her. Eurylochus suspects her treachery, and when she turns the rest of the expedition into pigs, Eurylochus escapes and warns Odysseus and the portion of the crew who stayed on the ship, thus enabling Odysseus to attempt a rescue. When Odysseus goes to save his men, Eurylochus refuses to guide him and urges him to escape and leave the men to their fate.
When Odysseus returns from Circe having rescued the men, Eurylochus insults Odysseus. Odysseus considers killing him but the crewmen drag them apart.
After making a truce with Odysseus, Circe advises him to see the prophet Tiresias for more advice to safely go back home. Tiresias later instructed Odysseus not to touch the cattle on the island of the sun god Helios, but Eurylochus convinced the hungry and mutinous crew to kill and eat some of them. As a punishment Odysseus' ship was destroyed and all of his crew, including Eurylochus, were killed in a storm sent by Zeus. Only Odysseus survives.