She's certainly far less well known than many of her contemporaries, but Noether's theorem is an incredibly important tool in theoretical physics, and has been described as "certainly one of the most important mathematical theorems ever proved in guiding the development of modern physics, possibly on a par with the Pythagorean theorem". [1]

[1]: http://en.wikipedia.org/wiki/Emmy_Noether#cite_note-FOOTNOTE...