This article briefly summarizes the information now available, from recent experiments,
computer simulations and theoretical models, addressing the outstanding mechanical properties
of graphene. In particular, experimental data on superior strength and extremely high in-plane
stiffness of pristine graphene are presented. The role of dislocations as carriers of plastic flow in
graphene is discussed. Special attention is devoted to the effects of grain boundaries in
polycrystalline graphene on its strength.Also, enhancement of fracture toughness due to graphene
inclusions in nanocomposites is considered. Finally, important unsolved problems in interdisciplinary
fundamental science and applied research of the mechanical properties exhibited by
graphene are outlined.