The Xiliens (Ｘエックス星人 Ekkusu Seijin, lit. X Star People) are a race of extraterrestrials who first appeared in the 1965 Godzilla film, Invasion of Astro-Monster.
Hailing from Planet X located just beyond Jupiter, the Xiliens are a technologically advanced race bent on conquering the Earth for themselves. In Invasion of Astro-Monster, the Xiliens pretended to be under siege by Monster Zero, their name for King Ghidorah, and reached out to humanity for assistance. After humanity allowed them to bring Godzilla and Rodan to Planet X to stop King Ghidorah, they revealed that Ghidorah had been their pawn the entire time and that they now had control over both Godzilla and Rodan. When mankind did not capitulate to their ultimatum that the Earth become a colony of Planet X, they unleashed all three monsters on Earth. However, human scientists were able to defeat the Xiliens using a special sound frequency and invented a device to sever their control over the monsters. Defeated, the Xiliens self-destructed their UFOs and base on Earth.
The Xiliens returned as the villains in Godzilla: Final Wars nearly four decades later. Intending to harvest the mitochondria from human cells for sustenance, they again posed as allies to humanity, unleashing an army of monsters under their control before teleporting them all away. When their plan was exposed by the Earth Defense Force, the Xilien Commander was assassinated and usurped by his subordinate who became the Controller of Planet X. The Controller unleashed all of the Xiliens' mind-controlled kaiju on Earth and tried to eliminate all resistance, but the surviving members of the EDF used the Gotengo to free Godzilla from his prison in Antarctica. Godzilla swiftly eliminated most of the Xiliens' monsters before the Controller summoned his ultimate weapon, Monster X, to stop him. The Gotengo breached the Xilien Mothership and its crew were able to defeat the Controller and his minions. In a final act, the Controller set the Mothership to self-destruct, but the Gotengo was able to escape in time and help Godzilla overcome Monster X's final form, Keizer Ghidorah.
The Xiliens are very popular antagonists in the Godzilla franchise and Toho's most famous alien race, having been featured prominently in films from both the Showa and Millennium series. Outside of their two film appearances, the Xiliens are frequently featured as the villains of various pieces of non-film media. They appear in video games such as Godzilla: Monster of Monsters! and Godzilla Defense Force, and are the recurring antagonists of the 1997 television series Godzilla Island. Additionally, the Xiliens are the inspiration behind the Exif race in the GODZILLA anime trilogy.
