Yavin 4 is one of the many moons of the gas planet Yavin in the Star Wars universe. It was home to the Rebel Alliance's main military base in Star Wars Episode IV: A New Hope. The Rebels established their base in the ancient Massassi ruins found in its lush jungles following the destruction of their previous base on the planet Dantooine. The Galactic Empire sought to use its new space station super-weapon, the Death Star, to destroy the small jungle moon and crush the Rebellion. A small force of X-Wing and Y-Wing starfighters were sent to destroy the Death Star, but most were killed in the attack. With seconds remaining and the timely assistance of his friend Han Solo, Luke Skywalker was able to fire a proton torpedo into a small thermal exhaust port along the Death Star's equatorial trench, thus destroying the station and saving Yavin 4. A great ceremony was held following the Death Star's destruction, where Princess Leia bestowed medals of honor to Luke Skywalker and Han Solo, along with his Wookiee co-pilot, Chewbacca.

This battle became known as the Battle of Yavin, and its date is used as a place-marker for events in the expanded Star Wars universe. Events before the Battle of Yavin are marked by BBY, and events that occur after are marked by ABY.

In the Expanded Universe, Luke later returns to the moon to found a Jedi academy there, rather than on Coruscant. The academy was destroyed by the Yuuzhan Vong in 26 ABY.

In Tales of the Jedi, it is stated that Yavin 4 was where Naga Sadow hid from the Republic in 5,000 BBY and was discovered a thousand years later by fallen Jedi Freedon Nadd. According to the comic series, the Massassi warriors who built the ruins used by the Rebels were brought to the planet by the early Sith.

In the young reader novel, The Lost City of the Jedi, it is discoved, as the title suggests, that the ancient Jedi built a lost city on Yavin 4. This city has not been seen in any other Star Wars work, due to the book's unpopularity.