William Nunn Lipscomb, Jr. (born December 9, 1919) is an American inorganic chemist, working in experimental and theoretical chemistry and biochemistry.

He was born in Cleveland, Ohio, and received his Bachelor of Science degree at the University of Kentucky in 1941 and his Doctor of Philosophy degree from the California Institute of Technology in 1946.

From 1946 to 1959 he taught at the University of Minnesota. Since 1959, he has been a professor of chemistry at Harvard University.

He deduced the molecular structure of boranes using X-ray crystallography in the 1950s and developed theories to explain their bondss. Later he applied the same methods to related problems, including the structure of carboranes on which he directed the research of future Nobel Prize winner Roald Hoffmann. His later research focuses on the atomic structure of proteins, particularly how enzymes work.

He was elected to the National Academy of Sciences in 1961, and awarded the Nobel Prize in Chemistry in 1976.