In Greek mythology, Eurylochus, or Eurýlokhos 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.

When the ship stopped on Aeaea, home of Circe the witch, Eurylochus was chosen by lot to lead a group of men to explore the island. After the crew spotted a column of snoke, Eurylochus led his group towards the smoke. They soon neared a palace surrounded with wild but benign animals. Inside the palace was Circe singing, and all of Eurylochus' party except for himself rushed inside to greet her. Eurylochus suspected her treachery from the beginning, and when she turned the rest of the men into pigs, Eurylochus escaped and warned Odysseus and the rest of the crew that had stayed on the ship, thus enabling Odysseus to save his crew.

However, Eurylochus often disagreed with Odysseus. Although Circe, after making a truce with Odysseus, later instructed Odysseus not to touch the cattle on the island of the sun god Helios, Eurylochus convinced the hungry and mutinous crew to kill 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 survived.

Eurylochus was also a Spartan general during the Peloponnesian War. He fought and was killed at the Battle of Olpae.