The rheological properties of magnetorheological (MR) materials, such as their viscosity and dynamic modulus, can be tuned or controlled by changing the intensity of the magnetic field using appropriate control schemes. Thanks to their robustness, performance and smart properties, numerous studies have been undertaken on the development of new MR materials, and microscopic and macroscopic modelling approaches. Novel applications include engine mounts and clutch systems in the automotive industry, shock absorbing safety devices for cockpit seats in aerospace, and shock absorption from movement in semi-active human prosthetic legs. This book introduces magnetorheological fluids and elastomers, and explores their material properties, related modelling techniques and applications in turn. The book offers insights into the relationships between the properties and characterisation of MR materials and their current and future applications, making it useful reading for researchers, engineers and graduate students who work in the field of smart materials and structures.