This review (with 200 references) summarises the state of the art of gas and vapour sensors based on the use of vanadium oxide (VO; with V occurring in various valencies) nanostructures. Following an introduction that covers the discussion of VO and their stable forms, the first large section covers experimental techniques employed for preparing VO nanostructures, with methods such as precipitation, hydrothermal synthesis, electrospinning, polyol techniques, laser deposition, and magnetron sputtering. The next section deals with VO-based sensors for oxidising gases such as nitrogen dioxide, carbon dioxide, oxygen, and ozone. We then discuss sensors for reducing gases and vapour, such as various alcohols, formaldehyde, hydrogen, methane, various amines, hydrogen sulphide, LPG, and neutral gases and vapours such as helium and humidity. An overview of the wealth of materials, methods, and sensing characteristics such as sensor response, analytical ranges, and operational temperatures is presented in Tables. The final section briefs the VO-based flexible sensors, followed by a concluding section that summarises the current status and challenges, and gives an outlook on potential future perspectives. Graphical abstract The state of the art of vanadium oxide nanostructures in gas/vapour sensing has been discussed in this work.