This chapter details the Glashow-Weinberg-Salam theory of electroweak unification, which combines the electromagnetic and weak forces using SU(2) and U(1) symmetries. It introduces the W and Z gauge bosons and the concepts of weak isospin and weak hypercharge. The text then addresses the mass problem for the weak bosons through spontaneous symmetry breaking and the Brout-Englert-Higgs mechanism. This approach successfully generates masses for the W and Z bosons while predicting the existence of the massive scalar Higgs boson. The chapter concludes by discussing the generation of fermion masses and reviewing the experimental evidence supporting the Higgs mechanism.