Mutants were first introduced to the Marvel universe by Stan Lee and Jack Kirby as a way to explain the recurring powerful abilities without resorting to scientific accidents, leading to the birth of the X-Men and the rise & fall of the mutant race that has developed into the thriving mutant island of Krakoa.
Recent storylines that have included Moira' shocking reveal of her previously unknown mutant ability in House of X, or Fantastic Four's recent game-changing news that long-standing omega-level mutant Franklin Richards actually isn't a mutant at all, highlight how easy it is to forget some of the other Marvel characters that are mutants.
10 Cloak & Dagger
Tyrone Johnson & Tandy Bowen were living on the street when they were kidnapped and experimented on using drugs that were designed specifically for addiction. The rest of the test group were killed by the drugs, but Ty and Tandy's latent mutant genes were activated to create Cloak and Dagger.
Cloak developed a connection to the Darkforce Dimension that existed within his cloak and allowed him to teleport, which was tempered by Dagger's light-based abilities that she could use as projectiles which also gave her limited psionic and healing abilities.
9 Red Guardian
While the original Red Guardian (who will make the jump to the big screen in the upcoming Black Widow) was empowered using a Russian super-soldier program much like the one that gave Captain America his abilities, there have been a few who have followed in his footsteps.
The current Red Guardian is the former Russian hero Vanguard, who works alongside his mutant sister Darkstar on the Winter Guard. Red Guardian's mutant power grants him a repulsive force field that he uses in various ways, including controlling his shield like his American counterpart.
8 Namor The Sub-Mariner
While he is frequently known as Marvel's first mutant (though chronologically that title belongs to more ancient characters like Apocalypse), Namor the Sub-Mariner isn't immediately recognizable to new fans as a mutant.
Namor's human/Atlantean parentage resulted in his unique mutant physiology, making him an outsider among those he rules. He rarely works with the X-Men save for their brief association with Atlantis during the Utopia era, and he was his usual rude and dismissive self when he was contacted about the development of the Krakoan society.
7 Abigail Brand
While the character of Abigail Brand first appeared in the pages of Astonishing X-Men as the powerful boss of the original S.W.O.R.D. organization that monitored alien threats to Earth, even the X-Men were unaware of her status as a mutant.
It was only through later encounters and battles that Brand revealed she was actually an alien/mutant hybrid with a pyrokinetic ability that allowed her to generate intense heat. Her alien heritage also gives her the ability to speak languages that humans can't, which will serve her well when she leads the newest iteration of S.W.O.R.D. following X of Swords.
6 Madame Web
While the current Madame Web is the former Spider-Woman Julia Carpenter, she inherited the title and abilities from Cassandra Webb after her death in order to help protect the Web of Life and Destiny that connects the various spider-characters in the Marvel multiverse.
As the original Madame Web, Cassandra's mutant abilities of telepathy and clairvoyance gave her the prophetic visions she used to help guide Spider-Man and other heroes on their totemic destiny, which she then passed on to Carpenter after her death during the "Grim Hunt" storyline.
5 Whirlwind
David Cannon/Whirlwind first appeared as a foe to Ant-Man and the Wasp before he began working against the Avengers on his own and with the Masters of Evil where he continued to redesign his costume to feature deadlier armaments.
However, while his armored costume appeared to the main aspect of his power, it's his mutant ability to generate fast-moving winds that made him a real threat – though those abilities were recently stolen by the Sin-Eater.
4 Kraven The Hunter
Sergei Kravinoff was the original Kraven the Hunter, and while he had enhanced his abilities with mystical and herbal potions and remedies, he was not a mutant. However, his son Alexei "Alyosha" Kravinoff eventually took over as Kraven, and he was revealed to be a mutant.
Alyosha shared similar enhancements as his father that increased his strength, speed and endurance, as well as enhanced senses and a regenerative healing factor. However, when Sergei turned on his family and demanded they fight each other for survival, he was allegedly killed by his sister Ana.
3 Typhoid Mary
When Typhoid Mary first appeared in the pages of Daredevil, she was a mysterious and well-trained mercenary who eventually revealed that she suffered from dissociative identity disorder, which had initially been unlocked after a fall from a window caused by Daredevil himself.
Mary Walker possesses a number of psionic abilities that included telekinesis and pyrokinesis, which were controlled independently by her Typhoid and Bloody Mary personalities. She later joined the Initiative as the masked Mutant Zero in order to gain control of her psyche, but soon returned to her Typhoid personality.
2 The Sphinx
While the majority of The Sphinx's powerful abilities come from his connection to the ancient Ka Stone that he bonded with centuries ago in ancient Egypt, Anath-Na Mut was also later revealed to have been one of the first mutants as well.
Although he was a gifted wizard before he found the powerful Ka Stone, Sphinx's classification as a mutant occurred in the pages of Doctor Strange: Sorcerer Supreme, which explored the alien Caretakers of Arcturus and their influence on Earth, including creating ancient mutants like the now-immortal Sphinx.
1 Santa Claus
What is both incredibly surprising but also makes a lot of sense is the fact that Marvel's Santa Claus is an established mutant, and one of the Marvel universe's most powerful mutants at that, as identified by Cerebro in the Marvel Holiday Special 1999.
His various mutant abilities are what enable him to perform his duties every year on Christmas, as well as other reality-altering abilities he displayed against the X-Men and the Brotherhood of Evil Mutants. He was more recently seen under the control of an evil elf when Deadpool was hired by angry children to assassinate Santa.