John Bennett Fenn (born June 15, 1917, New York City) is an American research professor of analytical chemistry who was awarded a share of the Nobel Prize in Chemistry in 2002.

He joined the Yale University faculty in 1962. In 1987, he reached the mandatory retirement age.
Fenn joined Virginia Commonwealth University in 1994 as professor of analytical chemistry, after more than 20 years at Yale University.
He was awarded the Association of Biomolecular Resource Facilities Award for outstanding contributions to Biomolecular Technologies in 2002.
The patent rights to electrospray ionization became the subject of a legal case between Yale University and Fenn, and on February 8, 2005 Yale was awarded over one million dollars and partial patent rights to the technique.