Who created Ultron?
If you go with the new movie Avengers: Age of Ultron...Tony Stark aka Iron Man. and Bruce Banner aka The Hulk!
If you go with Marvel Comics history...Henry Pym aka Ant-Man/Giant-Man/Goliath/Yellowjacket/Wasp/etc (Don't ask. It's too long a story...).
In reality, it was writer Roy Thomas and artist John Buscema in Marvel's Avengers V1 #54 (1967).
But where did Roy come up with the idea?
Well, he "borrowed" it from Captain Video!
In #3 of Captain Video's short-lived 1950s title, he faced a robot named Makino who killed his scientist creator and then threatened all mankind!
The story left such an impression on the young Roy Thomas that, almost two decades later, he adapted elements of that story into the long-running saga of Ultron!
Roy explained how it came about in TwoMorrows' Alter Ego #114.