Strain engineering is the process of tuning a material's properties by altering its mechanical or structural attributes. Atomically thin two-dimensional nanomaterials (2DNMs), which have been extensively studied in recent years, are particularly well-suited for strain engineering because they can withstand large strain. Thermal vibration, surface adhesion, substrate deformation, pre-stretched substrate, epitaxial grown, thermal expansion mismatch, substrate topography modification, pressurized blisters and tip indentation can lead to strain in 2DNMs. Strain in 2DNMs can modify their atomic structure, lattice vibration, thermal conductivity, electronic and optical, electrical and device performance, and chemical activities. This review focuses on the structural and mechanical properties of various 2DNMs, different experimental strategies to induce strain and modify properties, and applications of strained 2DNMs. Also, the review proposes prospective research areas for future strain engineering studies in 2DNMs. (C) 2018 Elsevier Ltd. All rights reserved.