For many years protein hydrolysates have been used in the food industry due to ability to modify the functional properties of proteins, mainly solubility, emulsifying and foaming features, flavour, etc. More recently, protein hydrolysates are incorporated as food ingredients in energy-providing drinks, hypoallergenic formulae, enteral diets for children and clinical nutrition. To this end, the nutritional properties are improved in comparison with native proteins. Among the various protein sources (soy, wheat, egg, haemoglobin, etc.) whey proteins are outstanding due to their high nutritional value, low bitterness (depending on the enzymatic process) and low antigenicity. Finally, whey protein hydrolysates constitute an excellent source of bioactive peptides, showing anti-hypertensive, immunological or antimicrobial activity, for instance. With respect to the manufacturing of whey protein hydrolysates, the enzymatic bioconversion processes are of increasing use in the production, transformation and valorisation of protein raw materials. Predominantly, industrial production is carried out in a classical batch reactor at controlled temperature. At the end of the reaction the enzyme is inactivated and remains into the final product. However, there are several disadvantages associated to this method, the high enzyme consumption being the main one. Hence, alternative operational procedures have been proposed, mainly enzyme immobilisation onto supports and the use of ultrafiltration membranes. Thus, membrane ultrafiltration of whey protein hydrolysate is aimed at: i) fractionating the hydrolysate in order to adjust its functional and nutritional properties, ii) remove the enzyme from the final hydrolysate and iii) recover and reuse the enzyme in further reactions if possible. Whey protein hydrolysates have received much attention after the Second World War (SWW). Patents dealing with whey protein hydrolysates have been issued regularly, particularly during the 1970s. Initially, the scope of such patents was to produce whey protein hydrolysates as food modifiers (improving protein solubility, providing emulsifying or foaming ability, etc.). During the 1980s and 1990s, patents were focused on reducing the antigenicity of proteins. For this purpose, it is essential to control the characteristics of the final hydrolysate. Hence, membrane technologies were used to obtain selected fractions and remove undesirable substances like free amino acids or non-reacted native proteins. Finally, selected peptides released during enzymatic degradation of proteins may regulate biological processes like hypertension mechanisms, immune reactions, etc. Thus, the manufacturing of bioactive peptides is a new research area and a number of recent patents have been published. In this article, a comprehensive review of the patents dealing with the enzymatic processes, membrane technologies and applications of whey protein hydrolysates is provided.