This book is designed as per NEP 2020 guidelines and is meant for undergraduate physics students. The text begins with a coverage of kinetic theory and dynamics of ideal gases and then proceeds to discuss real gases. Thereafter the basic formalism, zeroth law, first and second laws of thermodynamics are introduced. It concludes with chapters on thermodynamic potentials and Maxwell's relations as well as classical and quantum theory of black body radiation. Written in a lucid manner, students will require only a prior knowledge of mathematical concepts such as differentiation and integration to understand these topics. Each chapter is divided into sections and subsections for ease of comprehension. Special attention has been paid to the simplification of concepts by providing intermediate steps for difficult derivations. Chapters are supported by a rich pool of practice questions like multiple choice questions, short answer type questions, long answer type questions, and numerical problems.