In this chapter, we review the fundamental concepts and formulation of the thermomechanics of continuous media. First, we revise the expressions of the two first laws of thermodynamics for thermomechanical processes, that is, those with rates in temperature and strains as independent state variables. These equations constitute the generalization of the energy balance equation that was presented, particularized for the isothermal case, in Chap. “ Basic Elements of Continuum Mechanics ” [12]. Next, we introduce different thermodynamic potentials such as the internal energy density, the Helmholtz free energy density, and the dissipation density. The latter is expressed in terms of additional independent internal state variables that take into account history-dependent changes in the material’s internal microstructure. The associated thermodynamic fluxes are then defined as derivatives of the dissipation density with respect to the corresponding thermodynamic driver (internal variable). The next section introduces the fundamental principles for simple (local, non-graded) materials, which allows establishing the general constitutive equations for the rest of the state-dependent variables, stress and entropy, from the expression of the chosen thermodynamic potential and the fulfillment of the second law of thermodynamics. These expressions are finally applied to several examples: the first set includes two types of non-dissipative materials, specifically ideal fluids and elastic solids in thermomechanical processes, and then finishes with some numerical results on the behavior of biological tissue with anisotropic hyperelastic behavior; the second set concerns dissipative cases, and considers damage mechanics and nonlinear viscoelastic solids. Three numerical examples are presented: a metal plate with elastoplastic behavior, damage of a biological tissue, and a complex thermomechanical process involving the extrusion of an aluminum billet under high temperature and viscoplastic behavior.