Merck refers primarily to the German Merck family and three companies founded by the family, including:
the Merck Group, a German chemical, pharmaceutical and life sciences company founded in 1668
Merck Serono (known as EMD Serono in the United States and Canada), a pharmaceutical company headquartered in Darmstadt, Germany, and a brand and division of Merck focused on biopharmaceuticals
Merck & Co., Inc. (known as MSD (Merck Sharp & Dohme) outside North America), an American pharmaceutical company and a former subsidiary of the German Merck company, as founded in 1891/1917