Most landslides are triggered by rainfall. In previous studies, slope stability is often evaluated based on the infiltration analysis. Hydro-mechanical coupling is significant to rainfall-caused landslide evolution. This book covers theoretical models of unsaturated infiltration, and provides hydro-mechanical models for rainfall-induced landslides. The influences of rainfall patterns, boundary conditions, layered structures, and SWCC hysteresis on the coupled unsaturated infiltration and deformation are discussed. Laboratory testing of rainfall-induced landslides is performed to study the developing process of landslide upon rainfall infiltration. The results provide a better understanding of rainfall-induced landslides.