Fallout Shelter is a free-to-play mobile simulation video game developed by Bethesda Game Studios, with assistance by Behaviour Interactive, and published by Bethesda Softworks. Part of the Fallout series, it was released worldwide for iOS devices on June 14, 2015, and for Android devices on August 13, 2015. The game tasks the player with building and managing their own Vault, a fallout shelter.

A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War.