This main focus of this course is the theory of automorphic forms. Automorphic forms are a generalization of the idea of periodic functions in Euclidean space to general reductive Lie groups. The study of such functions is an important branch in representation theory and has applications in number theory. This course will start from a review of some basic topics includes Galois groups of number fields, decomposition subgroups, Dedekind zeta functions, Artin zeta functions, modular forms and Hecke algebras. We will then discuss Tate thesis, automorphic forms on classical groups and Langlands conjectures. Some knowledge about Lie theory such as Lie groups and Lie algebras is helpful to understand the course.