By now, most casual fans know the basic premise of Avengers: Infinity War. The alien supervillain Thanos goes on a quest to obtain all six of the cosmic Infinity Stones, which will give him unlimited power and allow him to wipe out half the life in the universe. But Thanos has a lot of work to do, because the last time fans saw him on screen — in the post-credits scene of 2015's Avengers: Age of Ultron — he had exactly zero Infinity Stones. So who has the Infinity Stones in Infinity War?
Before revealing which stone is where, it's important to have a little background on the stones themselves. The six stones are the remnants of what existed before the universe. In the Marvel Cinematic Universe, there existed six singularities before anything else. Once the big bang occurred, these six singularities were formed into Infinity Stones that represented their respective universal elements: Space, Power, Time, Mind, Reality, and Soul. The Space Stone wields power over the fabric of space, the Power Stone has immense destructive power, the Time Stone can affect time, The Mind Stone can control minds, the Reality Stone can warp reality, and the Soul Stone, which hasn't been seen yet on film, has the ability to collect people's souls and trap them within itself — at least in the comics.
So now that you know what the Infinity Stones are, here's where they are.
1
Space Stone
Also called the Tesseract, this was the first Infinity Stone seen in a Marvel movie. It was on Earth for a long time, and Loki was sent by Thanos in The Avengers to obtain it for him. Loki ultimately failed, of course, and the Tesseract ended up locked up in Odin's vault on Asgard. But in Thor: Ragnarok, Loki stole the Tesseract from Odin's vault before Asgard was destroyed, and he currently has it on the ship full of Asgardians — the ship that runs into Thanos' ship in that film's post-credits scene.
2
Mind Stone
The second stone seen in the MCU, the Mind Stone made its debut in The Avengers as part of Loki's scepter — which was lent to him by Thanos. In other words, Thanos had one Infinity Stone and gave it to Loki in the hopes of obtaining a second — but ended up with none. In Avengers: Age of Ultron, Ultron used the stone in his creation Vision, and today the Mind Stone still resides in Vision's forehead.
3
Reality Stone
The third Infinity Stone to be revealed was the Reality Stone in Thor: The Dark World, where it was called the Aether. This stone appears as a red mist rather than a stone, and in the post-credits scene from The Dark World, it was given to The Collector on Knowhere for safekeeping. As far as anyone knows, he still has it.
4
Power Stone
This stone made its introduction in Guardians of the Galaxy, where the Infinity Stones were explained for the first time. Once again, Thanos hired someone to obtain a stone for him — in this case, Ronan — and again, he ended up empty-handed. After Ronan was defeated by the Guardians, they gave the stone to the Nova Corps on Xandar.
5
Time Stone
Debuting in Doctor Strange, the Time Stone is also called the Eye of Agamotto. It's an ancient relic considered magical, and has likely been on Earth for hundreds, if not thousands of years. The stone is housed in a necklace, which Doctor Strange wears around his neck. He still possesses it.
6
Soul Stone
This is the only stone to not yet appear in the MCU, and as of right now, no one knows where it is. In the comics, it most often resided in the forehead of Adam Warlock, and while a post-credits scene of Guardians of the Galaxy: Vol. 2 hinted at Warlock's creation, it's unlikely he'll debut in Infinity War. For one, the movie already has a ton of characters and doesn't really have room for another super-important person. Secondly, Vision is already filling the role of "character with an Infinity Stone in his forehead" — something he does not do in the comics — so Warlock's inclusion would be redundant and possibly confusing.
Instead, it's more likely the Soul Stone is in Wakanda. It's known that Thanos invades the country in Infinity War, and he must have a reason for doing so. One Wakandan candidate for the Soul Stone is the mystical sand seen in Black Panther that allows people to speak to their dead ancestors, since it certainly seems in line with the powers of the stone seen in the comics.
With half the stones spread across the galaxy and the other half in the possession of powerful heroes on Earth, it seems Thanos has his work cut out for him in Infinity War.
