Actually, that is a very common misconception. Albert Einstein did **not** win the Nobel Prize for his work on the theory of relativity.

He was awarded the **1921 Nobel Prize in Physics** specifically for his discovery of the law of the **photoelectric effect**.

At the time Einstein was being considered, his theories of special and general relativity were still considered somewhat controversial and difficult to prove experimentally to the satisfaction of the entire Nobel committee. In contrast, his work on the photoelectric effect—which helped establish quantum theory by proving that light can behave as both a wave and a particle (photons)—was considered more definitively proven and practically significant. 

In fact, the presentation speech for his Nobel Prize actually mentions this, noting that he was awarded the prize "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."
