The idea of having a serious string theory course for undergraduates was first suggested to me by a group of MIT sophomores sometime in May of 200 I. I was teaching Statistical Physics, and I had spent an hour-long recitation explaining how a relativistic string at high energies appears to approach a constant temperature (the Hagedorn temperature). I was intrigued by the idea of a basic string theory course. but it was not immediately clear to me that a useful one could be devised at this level. A few months later, I had a conversation with Marc Kastner, the Physics Department Head. In passing. I told him about the sophomores' request for a string theory course. Kastner's instantaneous and enthusiastic reaction made me consider seriously the idea for the first time. At the end of 200 I. a new course was added to the undergraduate physics curriculum at MIT. In the spring term of 2002 I taught String Theory for Undergraduates for the first time. This book grew out of the lecture notes for that course. When we think about teaching string theory at the undergraduate level the main question is, "Can the material really be explained at this level?" After teaching the subject two times, I am convinced that the answer to the question is a definite yes. Although a complete mastery of string theory requires a graduate-level physics education, the basics of string theory can be well understood with the limited tools acquired in the first two or three years of an undergraduate education.