Ralph, a video game villain known for wrecking things in his arcade game, grows weary of being overshadowed by the game's hero, Fix-It Felix Jr. Frustrated at being condemned to the role of the bad guy and ostracized by the other characters in his game, he longs for recognition and a chance to prove he can be a hero too. Resolved to earn a medal and gain the respect of his peers, Ralph embarks on a journey across the arcade, hopping from game to game. His actions inadvertently unleash a dangerous enemy that threatens the safety of all the games in the arcade.

His first stop is Hero's Duty, a modern, high-definition shooter game, where he hopes to win a medal by battling cyber-bugs. It's there he meets the tough-as-nails Sergeant Calhoun, who's wary of his intentions. After a series of mishaps, Ralph accidentally finds himself in Sugar Rush, a candy-coated kart racing game. In Sugar Rush, he meets Vanellope von Schweetz, a quirky, glitchy character denied the chance to race by the game's ruler, King Candy. An unlikely friendship forms between the two outsiders as they strive to achieve their dreams amidst the colorful chaos of the various gaming worlds, unaware of the unintended consequences Ralph's game-hopping may have caused.