You are the sole survivor of a vault labeled Vault 71, a control vault that was originally intended to open up 30 years after the bombs dropped. But due to a change in leadership to a more power hungry overseer who had more nefarious intentions, that plan was secretly scrapped and was replaced with one to isolate the vault dwellers inside the vault and to prevent them from leaving, to ensure that he would have full control over them. The vault door is also stated to remain sealed shut at all times and that anyone caught attempting to open it will be heavily punished.

To ensure that no future overseer would be elected and risk exposing his plans to the residents, the overseer had his engineers build him a robobrain so that way he could live forever, or at the very least, a very long time.

As the years went on, the residents began to wonder when they would leave the vault to the outside world. They knew that they had to come out one day, but since so much time has gone by, they grew curious as to why they haven't left yet. When they asked the overseer on why they haven't opened the doors yet, he would always say something like "All of you will leave eventually, I can assure you. We just need to be sure that the outside world is safe enough to exit without any risk of harm." which would calm the vault dwellers. But only for a short period of time.

Unfortunately for them, in the year 2297, tragedy would arrive at their door step.

In the dead of night, remnants of a faction called The Enclave would arrive and demand for the vault door to be opened, to which the Vault-Tec staff would refuse. Seeing it as an act of resistance, The Enclave forcibly breaks through the vault and kills everyone inside the vault.

All except for you.

While you were unconscious, The Enclave remnants mistoke you for being dead and would leave the vault taking the G.E.C.K. with them.

As you awaken to find the entire vault in ruin and everyone inside dead, you venture out into the ruins of Missouri in search for the ones responsible for chaos for whatever intention you carry, whether it be for vengeance, justice, or for any other intention.