A process for the production of olefins from a hydrocarbon comprising the steps of: a) passing a first feed stream comprising gaseous reactants to a first reaction zone wherein said gaseous reactants react exothermically to provide a product stream b) producing a mixed feed stream comprising oxygen by passing the product stream produced in step (a) and a second feed stream comprising a hydrocarbon feedstock to a mixing zone, oxygen being passed to the mixing zone via (i) the product stream produced in step (a), (ii) the second feed stream comprising a hydrocarbon feedstock and/or (iii) a third stream comprising an oxygen-containing gas c) passing the mixed feed stream directly to an essentially adiabatic second reaction zone wherein in the absence of a supported platinum group metal catalyst at least a part of the oxygen is consumed and a stream comprising olefins is produced e) cooling the stream comprising olefins exiting the second reaction zone to less than 650.degree. C. within less than 150 milliseconds of formation and wherein the temperature of the mixed stream is at least 500.degree. C., the mixing zone and the second reaction zone are maintained at a pressure of between 1.5-50 bar and the residence time within the mixing zone is less than the autoignition delay for the mixed stream.