Sonic Adventure is a 1998 platform game for Sega's Dreamcast and the first main Sonic the Hedgehog game to feature 3D gameplay. It was ported to the GameCube in 2003 as Sonic Adventure DX: Director's Cut, featuring updated graphics and more challenges.

The story follows Sonic the Hedgehog, Miles "Tails" Prower, Knuckles the Echidna, Amy Rose, Big the Cat, and E-102 Gamma in their quests to collect the seven Chaos Emeralds and stop series antagonist Doctor Robotnik from unleashing Chaos, an ancient evil. Controlling one of the six characters—each with their own special abilities—players explore a series of themed levels to progress through the story. Sonic Adventure retains many elements from prior Sonic games, such as power-ups and the ring-based health system. Outside the main game, players can play minigames like racing and interact with Chao, a virtual pet.