|The following is based on Fallout 3 cut content and has not been confirmed by canon sources.|
Vault 100 is one of the Vault-Tec vaults which was due to appear in Fallout 3.
The Vault's original purpose in the vault experiment is unknown, or if it even was part of the experiment. The exact location of the vault is also unknown.
Vault 100 was referenced in the game files of Fallout 3 in the form of a Pip-Boy icon for an unimplemented Vault 100 jumpsuit. This icon is also present in the game files for Fallout: New Vegas as legacy content.