Vault Boy is the mascot of the Fallout media franchise. Created by staff at Interplay Entertainment, the original owners of the Fallout intellectual property, Vault Boy was introduced in 1997's Fallout as an advertising character representing Vault-Tec, a fictional megacorporation that built a series of specialized fallout shelters throughout the United States prior to the nuclear holocaust that sets up the world state of the Fallout universe. Within the video game series, Vault Boy serves as a representation of the player character's statistical information within user interface (UI) menus, and is a recurring element in Vault-Tec products found throughout the fictional Fallout universe. In the 2024 Fallout television series, Vault Boy is depicted as having been portrayed in Vault-Tec advertisements by actor Cooper Howard.

Fallout: A Post Nuclear Role Playing Game is a 1997 role-playing video game developed and published by Interplay Productions, set in a mid-22nd century post-apocalyptic and retro-futuristic world, decades after a nuclear war between the United States and China. Fallout's protagonist, the Vault Dweller, inhabits an underground nuclear shelter. The player must scour the surrounding wasteland for a computer chip that can fix the Vault's failed water supply system. They interact with other survivors, some of whom give them missions, and engage in turn-based combat.