Fluid flow at nanoscale is closely related to many areas in nature and technology (e.g., unconventional hydrocarbon recovery, carbon dioxide geo-storage, underground hydrocarbon storage, fuel cells, ocean desalination, and biomedicine). At nanoscale, interfacial forces dominate over bulk forces, and nonlinear effects are important, which significantly deviate from conventional theory. During the past decades, a series of experiments, theories, and simulations have been performed to investigate fluid flow at nanoscale, which has advanced our fundamental knowledge of this topic. However, a critical review is still lacking, which has seriously limited the basic understanding of this area. Therefore herein, we systematically review experimental, theoretical, and simulation works on single- and multi-phases fluid flow at nanoscale. We also clearly point out the current research gaps and future outlook. These insights will promote the significant development of nonlinear flow physics at nanoscale and will provide crucial guidance on the relevant areas.