Carlsberg Marston's Brewing Company is a British brewing company. It was formed when Marston's plc disposed of its brewing operations in 2020, selling the assets to a newly formed joint venture with the Carlsberg Group to create the Carlsberg Marston's Brewing Company (CMBC), in which Marston's plc holds a 40% share.

Brewing is the production of beer by steeping a starch source in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer, at home by a homebrewer, or communally. Brewing has taken place since around the 6th millennium BC, and archaeological evidence suggests that emerging civilizations, including ancient Egypt, China, and Mesopotamia, brewed beer. Since the nineteenth century the brewing industry has been part of most western economies.