The British Milk sheep is a robust, dual-purpose sheep commonly known for its milking characteristics.

The British Milk sheep originally was known as the Alderbred and is a breed of domesticated sheep developed by Lawrence Alderson and his wife Mary in Wiltshire and Northumberland. It was exported to several countries including Hungary, France and Greece, and from there other neighbouring countries. It now can be found mainly in the UK, Hungary and Canada, although the population in Britain was decimated during the outbreak of the foot-and-mouth disease in 2001. The exact composition of the breed has never been declared but it was based on high-performance animals in existing flocks of Dorset Horn, Bluefaced Leicester and Eastrip Prolific sheep kept by the Alderson family. Additional individual animals were selected from Lleyn, Texel and East Friesian breeds. The subsequent selection was based on measures of productivity, without regard for uniformity of appearance. A standardised breed type emerged gradually as the blending process continued. The animals were exposed to rugged conditions in the upper Pennines in northern England to develop robustness and adaptability. Progeny testing from the initial stages laid the foundation for continuous genetic improvement. Initially, total ownership of females of the breed was retained by the family and only rams were sold, but groups of females were released to other breeders in 1981. The numbers of flocks and animals increased rapidly and there were more than 5,000 breeding ewes by the mid-1980s with flocks widespread in Britain. A flock book was published in 1986. As the name of the breed suggests, it is a prolific milk producer, and several large dairy flocks were established. However, it is a robust, dual-purpose sheep rather than a specialist dairy breed. It is known for its extremely high prolificacy, and rams are used to sire high-performance crossbred daughters. The quality of its carcase and wool is extra beneficial traits. In all countries outside Britain, the British Milk sheep is used more as a dairying breed with dual-purpose qualities, but it is used also in most countries as a crossing sire; in Britain on hill and longwool breeds, in France in the Alps and Pyrenees on mountain breeds, in Greece on Chios dairy ewes, and Hungary on the predominant Merino population. In France, it has contributed to the development of the Boulonnais breed.

The British Milk sheep is a white-faced, clean-headed, polled sheep, with a large robust body that does well in conformation. At maturity, rams weigh 103 kg (227 lb) and ewes 79 kg (174 lb) on average. They have good carcase characteristics. In comparative trials in Hungary for meat production, crossbred lambs sired by British Milk sheep had a superior carcase grading, a higher killing-out percentage than crosses sired by Ile de France, Suffolk and Mutton Merino rams, and the meat was the most tender as measured by shear force.