Milk stout (also called sweet stout or cream stout) is a stout containing lactose, a sugar derived from milk. Because lactose cannot be fermented by beer yeast, it adds sweetness and body to the finished beer. Milk stout was claimed to be nutritious, and was given to nursing mothers, along with other stouts. Milk stout was also said to be prescribed by doctors to help nursing mothers increase their milk production. The classic surviving example of milk stout is Mackeson's,^[16] for which the original brewers advertised that "each pint contains the energising carbohydrates of 10 ounces [280 ml] of pure dairy milk". The style was rare until being revived by a number of craft breweries during the craft beer boom of the twenty-first century.

It is widely reported that, in the period just after the Second World War when rationing was in place, the British government required brewers to remove the word "milk" from labels and adverts, and any imagery associated with milk. However, no specific legislation or orders have been found to support this, though there were some prosecutions in Newcastle upon Tyne in 1944 under the Food and Drugs Act 1938 regarding misleading labelling.