This comprehensive text written for M.Sc. (Physics, Chemistry), M.Phil. (Physics) and B.Sc. (Hons) students aims at presenting the fundamentals of statistical mechanics in a clear and concise manner. In fourteen chapters, the book deals with all aspects of statistical mechanics: Thermodynamics, Microcanonical Ensemble, Canonical Ensemble, Grand Canonical Ensemble, MB Distribution, FD Distribution, BE Distribution for an ideal gas. The text also delves into certain topics of special interest, such as Interacting Systems, Phase Transitions, Kinetic Physics, Dynamic Theory of Gases, etc. The book concludes with an appendix on semiconductor statistics.