  These lectures provide an introduction to the basic ideas and methods of
Effective Field Theory, and a description of a few interesting phenomenological
applications in particle physics. The main conceptual foundations are discussed
in sections 2 and 3, which cover the momentum expansion and the most important
issues associated with the renormalization process. Section 4 presents an
overview of Chiral Perturbation Theory, the low-energy realization of Quantum
Chromodynamics in the light quark sector. The Chiral Perturbation Theory
framework is applied to weak transitions in section 5, where the physics of
non-leptonic kaon decays is analyzed. The so-called Heavy Quark Effective
Theory is briefly discussed in section 6. The electroweak chiral Effective
Field Theory is described in section 7, which contains a brief overview of the
effective Lagrangian associated with the spontaneous electroweak symmetry
breaking. Some summarizing comments are finally given in section 8.
