Process for the production of an olefin comprising partially combusting in a reaction zone a mixture of a hydrocarbon and an oxygen-containing gas in the presence of a catalyst which is capable of supporting combustion beyond the fuel rich limit of flammability to produce the olefin. The superficial feed velocity of the mixture is at least 250 cm s−1 at standard temperature and operating pressure, with the proviso that where the catalyst is an unsupported catalyst, the superficial feed velocity of the mixture is at least 300 cm s−1 at standard temperature and operating pressure. The process is carried out at a pressure of at least 1.3 bara and the reaction zone is not externally heated.