Donald Sharp "Don" Fredrickson (August 8, 1924 – June 7, 2002) was an American medical researcher, principally of the lipid and cholesterol metabolism, and director of National Institutes of Health and subsequently the Howard Hughes Medical Institute.
Fredrickson was born in Canon City, Colorado. His father was a county judge and the owner of Fredrickson Brown, an independent insurance agency. After high school he commenced medical school at the University of Colorado, but completed his studies at the University of Michigan after being transferred there by the army. During a cycling trip in the Netherlands he met his future wife, Priscilla Eekhof, and they married two years later. They would have two sons.
Between 1949 and 1952 he worked as a resident and subsequently as a fellow in internal medicine at the Peter Bent Brigham Hospital (now part of Brigham and Women's Hospital) in Boston. Much of his published work from this period is in the field of endocrinology. Subsequently he spent a year in the laboratory of Ivan Frantz, a cholesterol biochemist, at Massachusetts General Hospital.
In 1953 he took up a post at the National Heart Institute, part of the National Institutes of Health in Bethesda, Maryland. Initially, he worked with protein chemist and Nobel laureate Christian B. Anfinsen, and subsequently (with Daniel Steinberg) developed an interest in the metabolism of cholesterol and lipoproteins, as well as related medical conditions such as Niemann-Pick disease. His group identified Tangier disease (HDL deficiency) and cholesteryl ester storage disease, two inborn errors of cholesterol metabolism. He played a prime role in the identification of several apolipoproteins (proteins that characterise the nature of a blood lipid particle): APOA2, APOC1, APOC2 and APOC3.