Textbook in PDF format The coupled response of solid materials to multiple fields, such as deformation, heat, electricity, and magnetism, plays a crucial role in modern engineering applications, from soft robotics to energy storage. Advancing theoretical models and numerical implementations for these coupled behaviours in solids is a challenging and exciting frontier in mechanics. This textbook introduces some foundational coupled theories in solid mechanics by starting from fundamental principles of mechanics, thermodynamics, and electrodynamics, and specializing to model particular 'smart materials'. Numerous representative simulations are provided, demonstrating key coupled behaviours and engineering applications for each theory