This book provides a series of concise lectures on the fundamental theories of statistical mechanics, carefully chosen examples and a number of problems with complete solutions.Modern physics has opened the way for a thorough examination of infra-structure of nature and understanding of the properties of matter from an atomistic point of view. Statistical mechanics is an essential bridge between the laws of nature on a microscopic scale and the macroscopic behaviour of matter. A good training in statistical mechanics thus provides a basis for modern physics and is indispensable to any student in physics, chemistry, biophysics and engineering sciences who wishes to work in these rapidly developing scientific and technological fields.The collection of examples and problems is comprehensive. The problems are grouped in order of increasing difficulty.