In these 3 lectures, we give an introduction to Fourier Integral Operators (FIOs) with examples and applications. The lectures cover: wave front sets, Hormander-Sato Lemma, conormal distributions, Fourier integral distributions, symplectic manifolds and their Lagrangians, transverse and clean intersection calculus, symbol calculus, some estimates for FIOs and an introduction to I^{p,l} classes.