Astromech droids are a type of robot often encountered in the fictional Star Wars universe. Such robots are automated mechanics, doing many kinds of repair duties. Larger starships will usually carry a large complement of these in case of malfunctions or combat damage, although some stub-fighters (notably the X-wing and Naboo starfighter), carry a droid in a special port for in-flight field repairs. Astromech droids have also (in the Expanded Universe and computer games, at least) been known to carry out light janitorial duties, and the films have shown several instances of hacking (called "slicing" in Star Wars) being carried out by such droids, although this may require special programming to be installed. Most astromechs are apparently only able to communicate in writing, conveyed via another computer system, and a special code of clicks, bleeps and similar sound-effects. Possibly this is an attempt to minimize wasted space for speakers etc. Most human, humanoid or alien characters in the Star Wars universe seem to know this code by heart. The most prominent example is R2-D2, but there are other named examples, such as T3-M4, who appears in the Knights of the Old Republic computer game series and existed some 4000 years prior to the films. The T3 series shows considerable likeness to the R2 series, indicating that astromechs have not been subject to great change with time.

During the time period represented by the six Star Wars films, Industrial Automaton is by far the most successful manufacturer of astromech droids. They make the P2-, R1-, R2-, R3-, R4-, R5-, R6-, and R7-series. The R7-series is made specifically for use with the E-wing starfighter, while the others are for more general use.

Luke Skywalker briefly owned an E-wing and its associated R7 unit, R7-T1. He never felt very comfortable with either, though, and soon abandoned them both.

In Star Wars Episode II: Attack of the Clones, R4-P17 was the astromech droid attached to Obi-Wan Kenobi's Jedi Starfighter.