These Lecture Notes provide an introduction to classical statistical mechanics. The first part presents classical results, mainly due to L. Boltzmann and J.W. Gibbs, about equilibrium statistical mechanics of continuous systems. Among the topics covered are: kinetic theory of gases, ergodic problem, Gibbsian formalism, derivation of thermodynamics, phase transitions and thermodynamic limit.The second part is devoted to an introduction to the study of classical spin systems with special emphasis on the Ising model. The material is presented in a way that is at once intuitive, systematic and mathematically rigorous. The theoretical part is supplemented with concrete examples and exercises.