A conflict, specifically a war, occurred around 3900 BBY between the Gungans, who were native to the planet Naboo, and the Human Grizmallti colonists. These colonists, having escaped a violent civil war on their homeworld, encountered the Gungans just weeks after landing. Despite diplomatic efforts from both groups, they were unable to achieve peace. Consequently, the Gungans and Humans engaged in intense battles over land and resources for several decades thereafter.
Ultimately, a peace agreement was signed by both groups, in which they agreed to keep their distance from each other, all the while maintaining a strong sense of mutual distrust. As a consequence of this conflict, the Humans transformed their culture to prioritize peace, artistic expression, and the pursuit of knowledge, renaming themselves the Naboo. This hostility between the two groups lasted for many generations, until they eventually joined forces to fight off the Trade Federation during the Invasion of Naboo in 32 BBY.
The initial mention of the war between the Gungans and Humans appeared in Secrets of Naboo, which was a sourcebook released in 2001 for the Star Wars Roleplaying Game by Wizards of the Coast. However, various sources indicate that no war ever transpired between the Gungans and the Humans, including a statement made by Padmé Amidala in Star Wars Episode I The Phantom Menace, where she claimed that the two societies coexisted peacefully.
The DataBank in the 2001 LucasArts video game, Star Wars: Galactic Battlegrounds, also served as another source that contradicted the war's existence. During the game's development, the initial designs for the Gungan campaign included levels depicting a conflict between the Gungan Boss Gallo and tyrannical Human Naboo rulers. However, the creative team, which included level designer Stephen J. McManus, was informed that canonically, no such war had occurred between the two groups. As a result, McManus had to redesign the campaign to focus on a war between different Gungan tribes.
In 2004, the Star Wars Galaxies: Jump to Lightspeed: Prima Official Game Guide stated that despite their differences, the Humans and Gungans did not engage in warfare, but it did acknowledge that minor armed skirmishes were infrequent. Furthermore, the Knights of the Old Republic Campaign Guide, released in 2008, also challenged the war's existence, portraying the Gungans as "unperturbed" by the arrival of the Humans.