This book aims at giving the basis of primordial cosmology. The book is self-contained in the sense that all the elements for the derivations of the presented results are given. It can be used as a textbook to study cosmology. It is divided into 3 parts. Part 1 summarizes the fundamentals in theoretical physics needed in cosmology (general relativity, field theory, particle physics). Part 2 describes the standard model of cosmology and includes cosmological solutions of Einstein equations, hot big bang model, cosmological perturbation theory, cosmic microwave background anisotropies, lensing...