This chapter develops the Quantum Field Theory (QFT) formalism for Quantum Electrodynamics (QED). It begins with classical Dirac fields, deriving the Dirac equation and the free fermion/anti-fermion spinors. The quantization of the Dirac field is performed using anti-commutation relations to find the Feynman propagator for fermions. It addresses photon field quantization and the Gupta-Bleuler condition to handle gauge constraints. The full QED Lagrangian is then introduced, demonstrating local gauge invariance. Finally, the chapter establishes the Feynman rules and applies them to compute invariant amplitudes for fundamental QED processes like Bhabha scattering and Compton scattering.