"Bowser, also known as King Koopa, or Lord Bowser, is a video game character and the main antagonist of Nintendo's Mario series. In Japan, the character is known as Koopa (クッパ, Kuppa) and bears the title of Daimaō (大魔王, lit. "Great Demon King"). His Japanese name was also romanized Kuppa in earlier materials.
The leader and most powerful of the turtle-like Koopa race, Bowser is Mario's archnemesis, usually kidnapping Princess Peach and attempting to conquer the Mushroom Kingdom. Since his debut, he has appeared in almost every Mario series game."
Source: Wikipedia, "Bowser_(character)", available under the CC-BY-SA License.