- “Mutants, I don't hate them. I just know what they can do. You don't realize this but we are at war. I took an oath: Protect this country. My name is William Stryker, and I am not a monster. I'm simply a patriot.”
- ―William Strykersrc
William "Bill" Stryker Jr. is a covert operations specialist and military scientist. Known for his anti-mutant stance, he worked tirelessly over several decades to develop solutions to what he saw as the "mutant problem". Ironically enough, he himself was part of the problem as only males can pass the mutant gene to their offspring.
In 1973, Major William Stryker served as a personal assistant and bodyguard of Bolivar Trask. During the Vietnam War, William Stryker was an experienced helicopter pilot and flew many Black Ops missions into the jungles of North Vietnam, who sends him to an American airbase in Saigon, Vietnam where he attempts to subjugate several mutant soldiers, including Havok, Toad, Ink and Daniels to be brought in for experimentation at a Trask Industries laboratory. Mystique poses as an army colonel to interrogate Stryker's intention, and subdues him, taking the mutant privates back to America. Stryker tries to stop them escaping, to no avail.
A profound mutant-hater, William Stryker had served and protected his country for decades until he concluded that the main threat against the United States and its interests was not from opposing countries, but rather from within. Thinking the greatest threat to the world was mutants, Stryker became extremely paranoid and was dedicated to advancing the military to combat with these mutant problems should the need ever arise to, going by means of illegal experimentation on mutations. Though he has prioritised global and national security, Stryker has single-handedly caused social upheaval by implicating mutants in the assassination of the President of the United States in an attempt to turn them into public enemies so his attempted genocide on their species would be considered more acceptable. Stryker was also willing to kill his superiors if they went against his plans by murdering General Munson when he threatened to close the Weapon X Program.
Part of this intense hatred for mutants comes from Stryker birthing one himself. His son, Jason blamed him for his mutation, as it was usually passed along through the Y (male) chromosome. Furthermore, when he sent Jason to Charles Xavier's School for Mutants, Stryker believed his son was to be cured, only to discover that mutation was not a disease and this enraged Jason further, to the point where he tormented his mother and father to no end until Stryker's wife eventually committed suicide. Now with a personal incentive, Stryker's hatred only expanded until he set his goals on killing every mutant on Earth. Despite his hatred, though, Stryker found the usefulness of using mutants, at least those who he could control such as Lady Deathstrike, Nightcrawler and Cyclops. His basis on this was thinking that the only effective way to kill mutants was with mutants by building the ultimate mutant killer - Weapon XI. However, the original Team X was not mind-controlled with Sabretooth and Agent Zero being of their own free mind and will but it was presumably Wolverine, Wraith, Dukes, Wade and Bradley leaving that prompted Stryker to using mind control. Having studied mutants for years, he knew how to counteract with different threats opposed by individual mutants unique and varying powers such as building a plastic prison to contain Magneto, a device that prevents Professor X from taking control of anyone's mind and giving Lady Deathstrike an adamamtium skeleton and regenerative healing factor that was able to match and evenly duel with Wolverine, including adamantium nails similar to Logan's claws.
- Stryker is one of only two people who can see through Mystique's disguises, the other being Wolverine. Stryker sees through Mystique's abilities whilst she is imitating Wolverine to enter Stryker's base at Alkali Lake. He states that "if there's one thing I know better than anyone, it's my own work".
- William Stryker is the second-most recurring villain in the X-Men film series, second only to Magneto. Both men believe that the motivations behind their actions are for the greater good.
- Despite his apparent hatred for mutants, he frequently operates with military teams composed entirely of mutants. Examples are his formation of Team X, his creation of Deadpool, his control over Lady Deathstrike and the fact that he decided not to kill his son for being a mentally-ill mutant and for killing his wife.
- A notable discrepancy exists between the two portrayals of Stryker by Josh Helman and Danny Huston respectively; although Helman's incarnation is meant to predate Huston's, Helman only wears military decorations from the Vietnam War (1955-1975), whereas Huston wears decorations from the Korean War (1950-1953) and the Vietnam War.
- According to his military dogtags in Days of Future Past, William Stryker is a Protestant.
- In X-Men: Days of Future Past, Stryker has won the following military decorations (according to those apparent on his uniform):
- Silver Star (Ribbon) with "V" Valor Device
- Purple Heart (Ribbon)
- Meritorious Service (Ribbon) with "V" Valor Device
- National Defense Service (Ribbon)
- Vietnam Service (Ribbon) with Bronze Oak Leaf Cluster, indicating won twice
- Vietnam Campaign (Ribbon)
- Combat Infantry Badge
- Master Parachutist Badge (Army)
- Army Presidential Unit Citation
- His father, William Stryker Sr., has a minor role in X-Men: First Class. Stryker himself is mentioned by Xavier in passing, as his father was thinking about him during Xavier's meeting with the CIA.
- Bolivar Trask and William Stryker are the only characters to be dead in one timeline while in the other timeline they were In Custody for their heinous crimes.
- A deleted scene from X-Men: Days of Future Past presents an alternate take on Logan's recovery from the Hudson River at the end, wherein Stryker is asked what to call him, simply responding "Just call him... 'X' ", a reference to Logan's status as "Weapon X", the culmination of Stryker's mutant experiments to synthesize adamantium bonding to a mutant's exoskeleton to create the ultimate mutant soldier. Additionally, the Stryker that was featured during this alternate scene appeared to be the real William Stryker, and not Mystique posing as Stryker as was shown during the final scene of the theatrical cut.
- In X-Men: The Official Game, a mistake is made regarding Stryker's rank. Although he was referred to as a general in the game, the highest military rank he attained was that of colonel before his death in X2: X-Men United.
- In the comics, Stryker was a very different character from his film counterpart. He was a Christian televangelist instead of an army officer (though his comic book counterpart had a brief military stint) who hated mutants on a religious level based on his belief that all mutants are Satanic and are worthy of being exterminated in a holy war. He also founded a similarly minded para-military/terrorist hate group called the Purifiers for this purpose. This led to him being changed for the X-Men films to avoid any religious controversy.
- Originally in the comics Stryker was a one-time character that only appeared in God Loves, Man Kills graphic novel in 1982, but his success in X2 led to him and the Purifers being re-introduced into the mainstream comics.
- Stryker's film counterpart instead borrows elements from two other Marvel villains, Professor Andre Thorton, the man in charge of the Weapon X program, and Henry Peter Gyrich, (whom the film character Henry Gyrich was named after), who in the comics was a ruthless government official who sees mutants as very dangerous and uses his government resources to suppress them (as well as other superhumans).