Over the past 20 years, string theory has started to branch out and has tried to tackle difficult problems in several areas, mostly through the advent of the AdS/CFT correspondence. While at the beginning the sought-for applications were mostly in particle physics and cosmology, over the last 15 years or so we have seen a gradual increase in the number of applications to condensed matter theory, to the point that now various string theorists work completely in condensed matter. The purpose of this book is to provide an introduction to the various methods that have been developed in string theory for condensed matter applications, and to be accessible to graduate students just beginning to learn about either string theory or condensed matter theory, with the aim of leading them to where they can start research in the field. I assume a solid working knowledge of Quantum Field Theory, as can be obtained from a two-semester graduate course, and an advanced undergraduate course on Solid State physics, as well as some basic elements of General Relativity (but not necessarily a full course). Familiarity with string theory ormodern condensed matter theory is helpful, but not necessary, since I try to be as self-consistent as possible. To that end, in Part I, I give an introduction to modern topics in condensed matter from the perspective of a string theorist. In Part II, I give a very basic introduction to general relativity and string theory, mostly for the benefit of people who haven't seen them before, as they are not very detailed. Parts III and IV then describe the string theory applications to the condensed matter problems of Part I. The goal is to give an introduction to the various tools available, but I will not try to be extensive in my treatment of any of them. Instead, my aim is to have a fair overview of all the methods currently available in the field. Part III describes tools that are by now standard: the pp wave correspondence, spin chains and integrability, AdS/CFT phenomenology (“AdS/CMT”), and the fluid-gravity correspondence. Part IV focuses on more advanced topics that are still being developed, like Fermi liquids and non- Fermi liquids, insulators, the quantum Hall effect, nonstandard statistics, etc.