Mos Eisley is a spaceport town in the fictional Star Wars universe. Located on the planet Tatooine, it first appeared in the 1977 film Star Wars, described by the character Obi-Wan Kenobi (played by Alec Guinness) as a "wretched hive of scum and villainy".

A scene set in a seedy Mos Eisley cantina crowded with numerous alien races made a particular impact on audiences. Location filming for the spaceport took place from 1975 to 1976 in Tunisia, with interiors filmed at Elstree Studios near London.

Mos Eisley made its first appearance in the original 1977 film, Star Wars. It is depicted as a busy, bustling port city situated in a desert plain, populated with transients of all species. The lawless spaceport attracts criminals, smugglers and fugitives. Spacecraft land at docking bays dotted across the city.

The Mos Eisley scenes occur early in Star Wars, when the young hero Luke Skywalker and his mentor Obi-Wan Kenobi travel to the spaceport in Luke's landspeeder in search of a pilot, accompanied by the droids, C-3PO and R2-D2. Obi-Wan warns Luke that the spaceport may be dangerous. Upon arrival, Luke and Obi-Wan enter Chalmun's Cantina, a dimly-lit tavern patronised by visiting starship pilots. Strong drink is on sale at the bar and there are frequent outbreaks of violence among the clientele. The cantina attracts a range of exotic alien species, although droids are not permitted to enter; the bartender orders them to leave, saying "We don't serve their kind in here". A band of dome-headed aliens plays a set of jazz-style music. Luke is threatened with violence by two of the customers, Ponda Baba, an Aqualish, and Doctor Evazan, a deformed human and mentally unstable surgeon, but Obi-Wan intervenes with his lightsaber, severing Ponda's right arm in the fight. This is the first time a lightsaber is used in combat on-screen in the Star Wars franchise. Obi-Wan introduces Luke to a pair of smugglers, Chewbacca and Han Solo, and they negotiate terms for passage to the planet Alderaan, which prompts Luke to sell his landspeeder to get the money they need to pay Han. After Luke and Obi-Wan have departed, Han is involved in a brief confrontation with Greedo, a green-skinned gangster; the exchange ends violently when Han shoots and kills Greedo. As the group prepare to leave, they are followed to Docking Bay 94 by Garindan, a spy working for the Empire. Following a brief gunfight with Imperial stormtroopers, they board the Millennium Falcon spaceship and take off from Tatooine.

In the novelization of the film, Star Wars: From the Adventures of Luke Skywalker by George Lucas (ghostwritten by Alan Dean Foster), Mos Eisley is described as a haphazard, run-down settlement built of concrete and sandstone, a large part of it built underground to escape the heat of Tatooine's twin suns. The cantina is described as a dark, sinister bar full of "one-eyed creatures and thousand-eyed, creatures with scales, creatures with fur". The narrative describes "Tentacles, claws and hands... wrapped around drinking utensils".

The Expanded Universe anthology of intertwined short stories, Tales from the Mos Eisley Cantina, edited by Kevin J. Anderson, explores the cantina and its clientele further. The book names the establishment as "Chalmun's Cantina", introducing its proprietor as a Wookiee named Chalmun; it also reveals that the bartender is named Wuher. The book also explores the reasons for the cantina's ban on droids: the bartender claims to dislike everyone, but lashes out at droids because they are the only thing that will not try to fight back; the proprietor Chalmun does not tolerate droids because they do not drink, and therefore occupy valuable space. The backstory of the cantina's resident swing band is also expanded in the short stories "We Don't Do Weddings: The Band's Tale" by Kathy Tyers and "Empire Blues" by Daniel Keys Moran. The band is named as Figrin D'an and the Modal Nodes and it is revealed that the players belong to a race called Bith. Their main musical number is also given a title, "Mad About Me".

Mos Eisley appears in the 2019 Star Wars television series, The Mandalorian. In "Chapter 5: The Gunslinger", the Mandalorian is forced to set down in Mos Eisley for repairs after a space battle with another bounty hunter. In order to pay for the repairs, the Mandalorian goes to a local cantina to look for a bounty. There, he meets a rookie bounty hunter, Toro Calican, who hires him to help locate Fennec Shand, a dangerous mercenary. The pair locate Shand just beyond the Dune Sea and apprehend her. However, when the Mandalorian goes to retrieve transport for them, Shand tries to turn Calican against him by telling Calican about the Mandalorian turning against the bounty hunter guild to rescue the child. Calican mortally wounds Shand and decides to capture the Mandalorian and the child and collect all three bounties. The Mandalorian, however, is able to overcome Calican and rescue the child and Peli, a mechanic that was repairing his ship and watching the child. The Mandalorian gives Peli the reward for Shand as payment for the repairs and he and the child depart Tatooine.

The first view of Mos Eisley in Star Wars is a shot of Death Valley in California from the Dante's View lookout, with a matte painting added in the distance. The actual filming on location took place on the Tunisian island of Djerba.