"Some quotes from Albert Einstein, one of many great scientists who were not athiests:"

Albert Einstein is sometimes claimed by religious theists seeking the authority of a famous scientist for their theistic views, but Einstein denied the existence of the traditional concept of a personal god. Was Albert Einstein therefore an atheist? From some perspectives his position would be seen as atheism or no different from atheism. He admitted to being a freethinker, which in a German context is much the same as atheism, but it's not clear that Einstein disbelieved in all god concepts.

http://atheism.about.com/od/einsteingodreligion/tp/Was-Einstein-an-Atheist-.htm