This book is a comprehensive treatment of plasticity theory, intended as both a textbook for advanced undergraduate and graduate students and a primary reference for researchers in solid and applied mechanics. It addresses important developments in plasticity theory that have not been adequately covered in previous textbooks or monographs, including modern constitutive theories, continuum thermodynamics, large deformations, and numerical methods. Traditional topics such as elastic-plastic boundary value problems, slip line theory, and limit analysis are also included. The book contains eight chapters, with a generous number of exercise questions provided in each. Chapter 1 provides an extensive introduction to continuum thermomechanics, emphasizing constitutive theories of inelastic deformation from the viewpoint of internal variables. Chapter 2 introduces the physics of plasticity. The book is well-organized, self-contained, and provides a thorough foundation for understanding plasticity theory. It is suitable for both students and researchers, offering a comprehensive account of the field as it exists today.This book is a comprehensive treatment of plasticity theory, intended as both a textbook for advanced undergraduate and graduate students and a primary reference for researchers in solid and applied mechanics. It addresses important developments in plasticity theory that have not been adequately covered in previous textbooks or monographs, including modern constitutive theories, continuum thermodynamics, large deformations, and numerical methods. Traditional topics such as elastic-plastic boundary value problems, slip line theory, and limit analysis are also included. The book contains eight chapters, with a generous number of exercise questions provided in each. Chapter 1 provides an extensive introduction to continuum thermomechanics, emphasizing constitutive theories of inelastic deformation from the viewpoint of internal variables. Chapter 2 introduces the physics of plasticity. The book is well-organized, self-contained, and provides a thorough foundation for understanding plasticity theory. It is suitable for both students and researchers, offering a comprehensive account of the field as it exists today.