This chapter details the fundamental concepts of classical field theory, which serves as the prerequisite for field quantization. It begins by introducing the Lagrangian formalism for fields, where the dynamics are obtained from the action, the integral of the Lagrangian density. It then transitions to the Hamiltonian formalism, defining the canonical momentum and the Hamiltonian density. The chapter stresses the importance of using a covariant (relativistic) formalism to ensure consistency with special relativity. A central focus is the application of Noether’s theorem to fields, which directly links continuous symmetries of the action to conserved quantities, such as the energy-momentum tensor and conserved charges. Finally, the chapter applies this framework to derive and analyze the dynamics of simple relativistic field equations, notably the Klein-Gordon equation.