Fallout endings

Returned to normal Vault life
Prerequisites: Refuse to or fail trying to find the water chip.

Military Base
Prerequisites: Destroy the Military Base.

Cathedral
Prerequisites: Destroy the Cathedral.

Master's victory
Prerequisites: Join the Unity (reveal the location of Vault 13 to the Lieutenant or the Master), 500 days pass while the latter is alive (or 13 years regardless).

Ending 1
Prerequisites: Destroy the Military Base before taking the Cathedral.


 * The Vault Dweller's memoirs establish this ending as canon

Ending 2
Prerequisites: Destroy the Cathedral before the Mariposa Military Base.

NOTE: although the narrative plays out to be the other way around, the game is bugged to obtaining the opposite ending.

Water pump maintained
Prerequisites: Take the chip, fix the pump.


 * This ending is partially canon, as mentioned by some ghouls like Lenny in Gecko.

Dehydration
Prerequisites: Take the water chip, but don't fix the pump.

Mutant attack
Prerequisites: Enter Necropolis after 110 days have passed (30 after killing all the super mutants at the watershed).


 * The Vault Dweller's memoirs and Fallout 2 establish this ending as canon

Gain control of Boneyard
Prerequisites: Complete the Find Children spy in the Followers quest, but Heather's absence makes this impossible...and train the Followers in use of firearms.


 * Fallout: New Vegas establishes this ending as canon

This ending is bugged and cannot be obtained

Killed by mutants
Prerequisites: Don't find the Children spy in the Followers, or the Master is alive within 90 days (05 MAR 2162).

New California Republic
Prerequisites: Aradesh and Tandi are alive.


 * Fallout 2 and New Vegas establish this ending as canon

Aradesh grieves Tandi
Prerequisites: Tandi is dead or not rescued, Aradesh is alive.

Tandi takes over
Prerequisites: Aradesh is dead, but not Tandi.

Destroyed by raiders
Prerequisites: Both Aradesh and Tandi are dead (or the latter not saved from the Khans).

Razed by mutants
Prerequisites: The Master is still alive after 230 days have passed. Takes precedence over the other endings.

Junktown
In the original write-up of Junktown, the "ending sequence" was reversed from its final incarnation. See the alternate endings for the original versions, which were changed because the marketing department decided at the last minute that the game had to "reward good and punish bad".

Killian takes control
Prerequisites: Gizmo is dead, Killian is alive.


 * Fallout: New Vegas and J.E. Sawyer's Fallout Role-Playing Game establishes this ending as canon

Alternate version
[With the background picture being a gallows behind Killian with shadows of dead men hanging from it.]

Gizmo takes control
Prerequisites: Gizmo is alive.

Alternate version
[With the background picture showing Junktown as a Reno-like casino with electricity and clean streets free of any drug dealers or riff-raff who might endanger Gizmo's operations.]

Destroyed by mutants
Prerequisites: The Master is still alive within 210 days.

Drive mutants away
Prerequisites: Rhombus is alive.


 * Fallout 2, and post-Fallout 3, establish this ending as canon

Dictatorship
Prerequisites: Rhombus is dead.

Traitor
Prerequisites: Kedrick is alive, or the Master is alive for 170 days.

Prosperous trade center
Prerequisites: Complete the quest to find the missing caravans, but don't fulfill any of Decker's quests...Report Iguana Bob to the Hub police and be kind to Harold.


 * Fallout 2 and New Vegas confirm that this ending is canon.

This ending is bugged and cannot be obtained

Abandoned
Prerequisites: Do not complete the quest to find the missing caravans, complete at least one quest from Decker, or the Master is alive within 140 days.

Destroyed as a fighting force
Prerequisites: Kill Garl and at least eight more raiders, or kill at least thirteen raiders.


 * Fallout 2 and New Vegas establish this ending as canon (although a single Khan survivor, Darion, is found from Vault 15 in Fallout 2, where he is quite influental).

Regroup and terrorize
Prerequisites: Enter the raider camp but don't kill enough raiders for the previous ending.

Scourge that lasts for years
Prerequisites: Do not enter the main camp of the Khans.

Ending 1
Prerequisites: Take the Bloody Mess trait when creating your character (or picking up the Mutate! perk), procure bad Karma by the end of the game, or very quickly initiate combat upon exiting the conversation with Jacoren.

Ending 2
Prerequisites: Don't kill Jacoren.