All Terrain Walkers are armored fighting vehicles from the Star Wars universe that traverse the landscape on mechanical legs. They are used by the Old Republic, the Galactic Empire, and the First Order for ground assault, reconnaissance or transport. Throughout the saga walkers have played a pivotal role in the fate of characters and the outcome of battles. Industrial Light and Magic (ILM) is responsible for their animation and design, often using models, stop-motion animation, and relevant matte paintings to depict their presence in the films.

There are a variety of walkers: The Empire Strikes Back and Return of the Jedi introduced the All Terrain Armored Transport (AT-AT) and All Terrain Scout Transport (AT-ST). Star Wars: Episode II – Attack of the Clones, Star Wars: Episode III – Revenge of the Sith and The Clone Wars introduced earlier Clone Wars-era models of walkers, such as the All-Terrain Tactical Enforcer (AT-TE), and the All Terrain Recon Transports (AT-RT). The Star Wars Legends continuity features numerous walker variants, several which have been merchandised in popular culture, while the later films Rogue One and Star Wars: The Last Jedi depicted, respectively, the former the AT-ACT variant to the standard AT-AT, the latter a restyled AT-AT for its new and more modern setting, and a new, even larger walker known as the AT-M6.

The All Terrain Armored Transport (AT-AT) is a quadruped mechanized infantry combat vehicle used by Imperial ground forces.

The AT-AT (pronounced either casually as 'at at', or using only the letters 'A.T. A.T.') was first introduced in The Empire Strikes Back (as the Galactic Empire's main units against Rebel Alliance infantry during the Battle of Hoth) and also appears in Return of the Jedi and in Rogue One (in the AT-ACT variant).

The AT-AT also appears in a destroyed form in Star Wars: The Force Awakens, explained in the video game Star Wars Battlefront (2015) to be a residue of the Battle of Jakku, which was the Empire's last defeat and resulted in its dissolution, where Rey uses its husk for shelter. Updated forms appear in The Last Jedi (used by the First Order to attack Resistance forces in a former Rebel base).

The theme park attraction Star Wars: Rise of the Resistance, set after The Last Jedi, features two full-sized AT-ATs in a hangar bay. These walkers, while mostly static, can move their cannons to allow for a scene in which the walker's drivers spot the ride vehicles and fire at them.

Joe Johnston's original design for the Empire's war machines was a giant, multi-wheeled vehicle; this design later became the "Juggernaut" in West End Games' roleplaying material, and the design was reworked into the clone turbo tank for Star Wars: Episode III – Revenge of the Sith. Johnston said Lucas wanted the walkers to look like anthropomorphic walking tanks to make them frightening.

For The Empire Strikes Back, however, the final design was a four-legged walker. Inspiration for the AT-AT came from Paraceratherium, an extinct genus most closely related to living rhinoceroses, and one of the largest known land mammals. George Lucas later dismissed claims that the AT-AT design was inspired by container cranes at the Port of Oakland (across San Francisco Bay from ILM's San Rafael offices), calling it a "myth"; animator Phil Tippett told the San Francisco Chronicle the same thing.