Constitutive modeling is the mathematical description of how materials respond to various loadings. This is the most intensely researched field within solid mechanics because of its complexity and the importance of accurate constitutive models for practical engineering problems. The topics covered include: Elasticity, Plasticity theory, Creep theory, The nonlinear finite element method, Solution of nonlinear equilibrium equations, Integration of elastoplastic constitutive equations, The thermodynamic framework for constitutive modeling Thermoplasticity, and Uniqueness and discontinuous bifurcations.