In Greek mythology, Eumaeus, or Eumaios, was Odysseus' swineherd before he left for the Trojan War.

In the Odyssey, Eumaeus is the first person Odysseus meets after his return to Ithaca. Although he doesn't recognize his old master in disguise, Eumaeus still treats him well, giving him food and shelter. Eumaeus also welcomes Odysseus' son Telemachus when he returns from his voyage to Pylos and Sparta and Telemachus also does not recognize his father at first. During Odysseus' absence Eumaeus had acted as a father to Telemachus.

Despite being a swineherd, Eumaeus was fairly wealthy and could afford to buy his own slave. However, the suitors of Penelope had abused him, taking his best pigs for their own feasts and leaving him with only piglets to eat. Later, when Eumaeus finally recognizes Odysseus, he helps Odysseus kill the suitors.

Interestingly, Eumaeus is the only character in the Odyssey who is referred to in the second person, δι Ευμαιη, "you, Eumaeus." He is also frequently called the "noble swineherd."