Furfural is produced from biomass material containing pentosan, in high yields, in a production process comprising treating the biomass with a solution containing at least one α-hydroxysulfonic acid thereby hydrolyzing the biomass to produce a product stream containing at least one C5-carbohydrate compound in monomeric and/or oligomeric form, and dehydrating the C5-carbohydrate compound in the presence of an acid, in a biphasic reaction medium comprising an aqueous phase and a water-immiscible organic phase, at a temperature in the range of from about 100° C. to about 250° C. to produce a dehydration product stream containing furfural. An aqueous stream is separated from the dehydration product that can be optionally recycled to the hydrolysis step.