Finite temperature field theory

These lectures review phases and phase transitions of the Standard Model, with emphasis on those aspects which are amenable to a first principle study. Model calculations and theoretical ideas of practical applicability are discussed as well. Contents: 1.Overview; 2. Field Theory at Finite Temperature and Density; 3.Critical Phenomena; 4.Electroweak Interactions at Finite Temperature; 5. Thermodynamics of Four Fermions models; 6.The Phases of QCD; 7.QCD at Finite Temperature, $\mu_B = 0$; 8.QCD at Finite Temperature, $\mu_B \ne 0$.