This chapter describes the complex geomechanical and environmental conditions encountered in deep rock engineering and the mechanical characteristics of rocks when subjected to high in-situ stresses. It elaborates on the definition, formation mechanism, disaster levels, and prediction, as well as the prevention and control technologies for rockbursts of hard rocks and large deformation of soft rocks. The impact of high geothermal temperatures on the physical and mechanical properties of rocks, and their effects on rock engineering applications, are also discussed.