Supersymmetric Quantum Field Theories provide an exciting arena for exploring physics in the strong coupling regime. Supersymmetric localization has turned out to be a formidable tool for making progress in this direction. The goal of these lectures is to provide a concrete example of supersymmetric localization in the context of three-dimensional gauge theories. I will first review the basic idea of localization in the finite-dimensional case. I will then show an application of this idea to supersymmetric Chern-Simons matter theories. In particular, I will explain how matrix models capture the partition function of these theories.