Constitutive modelling is an important subject in continuum mechanics. This course focuses on the physical and mathematical principles of constitutive modelling with emphasis on soil mechanics. Elasticity and plasticity frameworks for isotropic and anisotropic soil modelling are discussed. Critical state hardening models such as the original Cam clay and modified Cam clay are elaborated in details. The concept of bounding surface and more advanced state-dependant dilatancy models are introduced. The course aims at providing students a fundamental understanding of the constitutive modelling techniques in soil mechanics.