I'm talking about the Pre-Crisis version. Most accounts say that Superboy was created without the permission of Jerry Siegel and Joe Shuster (the original creators of Superman). But if Siegel and Shuster didn't create the Boy of Steel, who did? :?:
As Super Monkey said, Siegel first came up with the idea for Superboy, but if you want to know who created the character of Superboy, as we knew him pre-Crisis, you'd have to say writer Don Cameron with editor Whitney Ellsworth. Cameron wrote the first Superboy story for More Fun Comics.
Siegel and Shuster can hardly have been too shocked at its appearance though, because it's generally accepted that Shuster contributed to the artwork.
Having said all that, of course Siegel and Shuster will always be the true creators of any version of Superboy, because he is just a young Superman.