The Odyssey picks up the story of Odysseus 10 years into his journey home from the Trojan War, which itself had lasted 10 years. The story opens with Odysseus being held captive by the goddess Calypso on a remote island. Back in his home city, Ithaca, his wife, Penelope, is being besieged by suitors, who have moved into her home, taking advantage of the ancient Greek custom of hospitality. Telemachus, son of Odysseus and Penelope, must watch the suitors take over their house, waiting for Penelope to choose a new husband. All—except Penelope—assume Odysseus is dead after his 20-year absence.
Athena, the goddess of war, has been watching over Odysseus since the Trojan War. She feels protective toward him and asks Zeus to help her free Odysseus from Calypso's island. Zeus sends his son Hermes to aid Odysseus in his escape. At the same time, Athena goes to Ithaca to offer help to Penelope and Telemachus. She advises the son to leave Ithaca to find information on the whereabouts of his father. The suitors take note of the newfound courage and authority that Telemachus displays, and they conspire to murder him when he returns to Ithaca. On his visit to King Menelaus on the island of Sparta, Telemachus learns that Odysseus is alive.
Hermes helps free Odysseus, who sails to the land of the Phaeacians. Exhausted, he collapses on the shore, where the princess Nausicaa discovers him. She leads him to the king, Alcinous, and his queen, Arete. There Odysseus tells them the story of his travels thus far. He and his men had run into a number of trials on their way home to Ithaca. They nearly lost themselves and their memories in the land of the Lotus-eaters and then incurred the wrath of Poseidon by blinding his son, the Cyclops Polyphemus. Odysseus and his crew were given a pouch full of sailing winds by Aeolus, but curiosity got the best of his men and they accidentally released the winds, which blew them off course and far from home. They encountered cannibals and witches, Odysseus visited the Land of the Dead, they avoided the lure of the deadly songs of the Sirens, and they escaped from numerous monsters. Odysseus lost his men one by one, and the rest were wiped out when they ate the cattle of Helios, which the blind prophet Tiresias had warned Odysseus about. They were punished by a single lightning bolt sent down by Zeus, which destroyed Odysseus's ship. He washed ashore on the island of Ogygia, where Calypso held him captive for seven long years.
Hearing the stories of Odysseus's journey, King Alcinous comes to his aid by providing him with a ship. Athena also helps Odysseus once again, forewarning him of the chaos at home in Ithaca and informing him that the worst is yet to come. She disguises Odysseus as a beggar and tells him to stop in at the farm of his old friend, the swineherd Eumaeus, before he goes to his house. She also orchestrates the reunion between Odysseus and Telemachus, whom she has advised to come home. Telemachus relates to Odysseus the behavior of the suitors, and they plot the mass murder of the suitors to restore honor to their home.
A few characters begin to recognize Odysseus through his disguise—among them his childhood dog Argos and his childhood nurse Eurycleia. However, his wife, Penelope, does not recognize him. When the suitors encounter Odysseus disguised as a beggar, they are cruel to him, taunting him and making him fight another beggar. But Odysseus is able to practice restraint and bide his time until his plan can be enacted. Penelope declares that she will hold a contest to choose her next husband—whoever can master Odysseus's bow to shoot down a row of axes will win. When the contest begins, none of the suitors can so much as string the bow.
The still-disguised Odysseus volunteers to undertake the challenge, to the chagrin of the suitors, but Penelope allows him to try. He strings the bow and shoots through the axes easily. The suitors are shocked, and Odysseus, taking advantage of their confusion, begins to kill them and the serving women who helped them. Athena once again offers aid, and Telemachus and loyal servants join in as well. Finally, Odysseus and Penelope are reunited, but not without a final test on the part of Penelope to ensure Odysseus's identity. However, they cannot live happily ever after just yet—the families of the slain suitors want revenge. The gods finally intervene, with both Athena and Zeus commanding peace. Odysseus's final journey is to see his father and then to offer a sacrifice to Poseidon, so that the god will leave him and his family in peace.