Ready Player One plot's

In 2045, people seek regular escape from life through the virtual reality entertainment universe OASIS, co-created by James Halliday and Ogden Morrow of Gregarious Games. After Halliday's death, a pre-recorded message left by his avatar Anorak announces a game, granting ownership of OASIS to the first to find the Golden Easter Egg within it which is locked behind a gate requiring three keys. The contest has lured a number of ‘gunters’, or egg hunters, and the interest of Nolan Sorrento, the CEO of Innovative Online Industries (IOI) who seeks to control OASIS himself. IOI uses a number of indentured servants and employees called "Sixers" to find the egg.^[a]

Wade Watts is an orphaned teenager living in the slums, or ‘stacks’, of Columbus, Ohio, with his Aunt Alice. In the OASIS, his avatar, Parzival, is best friends with Aech, a virtual mechanic. One day, Parzival befriends Art3mis, a well-known Gunter, sharing a common interest in Halliday's history. They review Halliday's life from the Archives with help of its Curator. They learn Halliday had several regrets in life, including his unrequited love for Morrow’s wife Kira and losing Morrow as a friend after forcing him to sign away his part of Gregarious Games. Using this information, they solve the first two challenges of Anorak's game: a car race across an ever-shifting Manhattan cityscape and a search for Kira in the Overlook Hotel from The Shining. Aech and his friends Daito and Sho follow suit, the five becoming known as the "High Five" on the OASIS scoreboards.

Sorrento learns of Parzival's identity through OASIS mercenary i-R0k, and attempts to sway Wade into joining IOI, but he refuses. In retaliation, Sorrento has IOI's head of operations F'Nale Zandor bomb Wade's stack, killing Alice. Art3mis' player, Samantha Cook, rescues Wade, but they are soon found by IOI. Samantha is captured and forced into IOI's servitude, while Wade is extracted by the other High Fivers – Helen (Aech), Toshiro (Daito), and Zhou (Sho). The group tracks down Samantha's location at IOI, and they remotely help her escape, allowing her to assist them in the OASIS as Art3mis.

The third challenge requires one to play Halliday's favorite Atari 2600 game, in a castle on Planet Doom, which Sorrento has protected with a force field. Parzival recruits other OASIS players to help the rebels attack the IOI forces around the castle. Art3mis deactivates the force field, allowing Parzival to reach the console, but Sorrento activates the Cataclyst, a bomb that kills all the avatars on Planet Doom. However, due to having won a coin from the Archive's Curator earlier, Parzival gets an extra life, proceeding to play through Adventure to find its Easter egg; he is awarded the last key. Opening the gate, he is greeted by Anorak and given a contract to sign; however, he recognizes it as the same contract Morrow signed to turn over his part of Gregarious and refuses. Anorak changes forms to be Halliday, revealing that the contract was the final test to make sure Parzival would not make the same mistakes he did. Parzival is given the Golden Egg and control of OASIS.