What scientist is credited with developing the continental drift theory?
The credit is mainly given to Alfred Wegener.
The credit for continental drift is mainly given to Alfred Wegener. After noting that Africa and South America seemed to fit perfectly together, he read papers from other scientists to learn more about what he assumed could not be a coincidence. In 1915, he formally wrote about his ideas in the book, "The Origin of Continents and Oceans."
You can read more about Wegener and the history of continental drift here.