Based on the author's graduate course taught over many years inseveral physics departments, this book takes a 'reductionist' viewof statistical mechanics, while describing the main ideas andmethods underlying its applications. It implicitly assumes that thephysics of complex systems as observed is connected to fundamentalphysical laws represented at the molecular level by Newtonianmechanics or quantum mechanics. Organised into three parts, thefirst section describes the fundamental principles of equilibriumstatistical mechanics. The next section describes applications tophases of increasing density and order: gases, liquids and solids;it also treats phase transitions. The final section deals withdynamics, including a careful account of hydrodynamic theories andlinear response theory. This textbook is suitable for a one yeargraduate course in statistical mechanics for physicists, chemistsand chemical engineers. Problems are included following eachchapter, with solutions to selected problems provided.