The Kree-Skrull War, in the fictional Marvel Universe, was a series of conflicts between the Kree Empire of the Greater Magellanic Cloud and the Skrulls of the Andromeda Galaxy that lasted for several million years.

The Skrulls were an advanced, benevolent race from the planet Skrullos, that first ventured outside their galaxy some ten million years ago and sought to build an intergalactic federation based on trade. On the planet Hala they encountered the Kree, an industrialized humanoid race, and the Cotati, a race of sentient plants. The Skrulls proposed a test to determine which race was worthy to join them.

The Skrulls took a group each of Kree and Cotati to a barren planetoid in the Milky Way galaxy, Earth's moon, and bade the two groups to create something of worth. The Skrulls then departed. The Kree constructed a magnificent blue city while the Cotati cultivated a beautiful garden.

A year later, the Skrulls returned and their emperor Dorrek judged the Cotati the winners. The Kree were outraged, slaughtering the Skrulls and Cotati and seizing the Skrull starship. Due to the immense distance between Hala and the Skrullos, news of the atrocity had not reached the Skrulls until the Kree had sufficient time to master the stolen technology.

Decades later, the Kree ventured into the Andromeda Galaxy, attacking Skrull outposts and finally Skrullos itself. This led the Skrulls to abandon their peaceful ways and become increasingly militaristic to combat the Kree threat.

The Kree built a supply outpost on Uranus, hoping to maintain a weapons base close to this strategic site. From this vantage point, the Kree learned of the vast genetic potential of Earth's people. Kree scientists travelled to Earth in order to perform their own experiments on the natives and develop a breed of super-soldiers to aid their war effort. The scientists created the highly-evolved sub-species called the Inhumans. Subsequently the Kree administration dropped their immediate plans to use the Inhumans as militia, although they would millennia later attempt to do so. The Kree stationed a Sentry robot on Earth to monitor the Inhumans' progress and any Skrull activity.

Although the Kree never launched an invasion of Earth, a skirmish in the Kree-Skrull War did occur recently in the Sol system, involving over a dozen of Earth's superheroes, notably the Avengers and Rick Jones.

Skrull Empress R'kill and the Kree Supreme Intelligence believed that the war had reached a stalemate and proposed a final resolution through single combat between the Skrull warrior Raksor and the Kree soldier BelDann . The Fantastic Four and the Inhumans goaded the combatants until they joined forces to ward off their attackers. The arbiter of the battle, Uatu the Watcher, commented that their willingness to cooperate demonstrated that the Kree and Skrull could work together too. Since this time, there has been no major resumption of hostilities.

Space in the Marvel Universe is dominated by three superpowers: the Shi'ar Empire, the Skrulls, and the Kree. The Devourer of Worlds, Galactus, destroyed the Skrull homeworld, Skrullos. Remaining Skrull territory factionalized, and the odds of victory were firmly tipped in favor of the Kree. However, the Skrull survivors tricked the Shi'ar Empress Lilandra into attacking the Kree with a "Nega Bomb" that killed 90% of the Kree population. The Shi'ar then conquered the survivors.

Thus, the Kree have been decimated and the survivors have been conquered by the Shi'ar; the Skrulls are too divided to pose a significant threat. So, in all likelihood, the Kree-Skrull War has come to an end and the Shi'ar Empire has been left as the last remaining intergalactic "super power" in the Marvel Universe.