The Marvel Universe is full of alien threats and armies, many with distinct elements that make them stand out from the rest of the cosmic corner of the universe. Many of them have even made the leap to other media from their place in the Earth-616 universe that gave birth to the Avengers and the rest of Marvel's heroes.

However, there's one distinct race, the Chitauri, that didn't make their introduction the typical way -- and instead debuted in another reality and in other media before they even arrived in the core universe. Now, how the Chitauri first appeared in the Ultimate Marvel Universe and the MCU's Avengers before they ever once appeared on Earth-616.

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Who Are the Chitauri in the Ultimate Marvel?

Ultimate Thor and Iron Man fighting the Chitauri fleet

The Chitauri were introduced in The Ultimates by Mark Millar and Bryan Hitch. An alien threat that had endeavored to conquer humanity during the course of World War II, the Chitauri had their plans halted by the efforts of Captain America and his allies. Defeated but not destroyed, the Chitauri on Earth moved into the shadows and infiltrated many aspects of humanity for decades, including S.H.I.E.L.D.

Effectively serving as the Skrulls for the Ultimate Universe, the Chitauri came close to conquering the world by attempting to destroy the titular heroic team and their allies in S.H.I.E.L.D. However, the heroes were able to survive a trap -- allowing them to assault the assembling Chitauri armies and overwhelm them. Coupled with other defeats across the galaxy, the Chitauri of the Ultimate Universe was more or less defeated once and for all by their loss on Earth.

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Who Are the Chitauri in the MCU?

Chitauri Soldier Avengers 2012

On Earth-199999 -- aka the Marvel Cinematic Universe -- the Chitauri had a more straightforward approach to combat. The alien horde was a collection of soldiers and massive Leviathans who served at the command of Thanos. In Avengers, Loki was able to strike a bargain with Thanos, recovering the Tesseract (secretly the Space Stone) on Earth in exchange for the service of the Chitauri army during his attack on Earth. Opening a rift in space, the Chitauri were able to assault New York City but were held at bay and repelled by the newly formed Avengers, thanks to a knockout blow from Iron Man.

Connected to one another via a crucial neural link that seemed to give the Chitauri an almost hive-mind-like quality, this pivotal aspect of the MCU's Chitauri was severed when Iron Man successfully dragged a nuclear weapon through the rift to destroy the Chitauri mothership. The remnants of this race were part of Thanos's army in Avengers: Endgame, and like the rest of his forces, were reduced to dust by Iron Man wielding all six Infinity Stones.

Who Are The Chitauri in the Marvel Universe?

Captain Marvel Secret Empire Chitauri

The Earth-616 incarnation of the Chitauri made their debut in Nova #3 by Jeph Loeb and Ed Mcguinness. Established as long-time enemies of the Nova Corps, the Earth-616 Chitauri operated even more like an insectoid race than in their previous appearances, with a defined queen commanding their number (or whoever claimed command of them via combat). They played a role in Secret Empire as one of the threats brought to Earth by the HYDRA-corrupted version of Captain America and were able to rally an army nearly capable of overwhelming the defenses of the planet.

Luckily for humanity, Captain Marvel -- who had been trapped outside Earth and led the defense against the invasion -- located and destroyed Chitauri Queen eggs being held by the evil Rogers' forces, sending the armada retreating back into the cosmos. They've since appeared in various cosmic Marvel storylines, including the build-up to Infinity Wars. After debuting in the Ultimate Universe and making a memorable appearance in the MCU, the Chitauri finally found their place in the core Marvel Universe over ten years after they were created.

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