The Proca Lagrangian is a fundamental concept in Quantum Field Theory (QFT) that describes the dynamics of a massive vector field (a field associated with a particle of spin-1 that has mass). It is named after the Romanian physicist Alexandru Proca, who first formulated it. The Proca Lagrangian is particularly important in the study of massive gauge bosons, such as the WW and ZZ bosons in the Standard Model of particle physics.