This book - the third in a set, following two standalone companions that introduce standard techniques of statistical mechanics - is a new edition of Problems on Statistical Mechanics (D. A. R. Dalvit et al, 1999, CRC Press).A thorough understanding of statistical mechanics depends strongly on the insights and manipulative skills that are acquired through the solving of problems. This book provides 268 problems with model solutions, illustrating both basic principles and applications.The problems occupy fourteen chapters, progressing from the simpler aspects of thermodynamics and equilibrium statistical ensembles to the more challenging ideas associated with strongly interacting systems and nonequilibrium processes.Each chapter consists of exercises spanning multiple levels of difficulty, from warm-up derivations to longer problems that connect several ideas. The solutions are written to be instructive rather than minimal and, in several places, include short contextual remarks - why a technique matters, what it is used for elsewhere, and how it relates to alternative approaches.The exercises are based on the content of the first two volumes of this set: - F. Caravelli and D. A. R. Dalvit, Practical Statistical Mechanics: Thermodynamics and Statistical Mechanics, Volume 1, CRC Press (2026). - F. Caravelli, J. Zanella Béguelin, and D. A. R. Dalvit, Practical Statistical Mechanics: Advanced Statistical Mechanics, Volume 2, CRC Press (2027). Key features: - Contains over 600 pages of worked problems in statistical mechanics and thermodynamics. - Comprehensive solutions to all problems are designed to illustrate efficient and elegant problem-solving techniques. - Serves as a reliable companion to studying the topic: something to consult when you are stuck, to compare approaches, and to learn what a complete solution looks like in this subject.