Ronald Björn Jensen (born April 1, 1936) is an American mathematician who lives in Germany, primarily known for his work in mathematical logic and set theory.

Jensen completed a BA in economics at American University in 1959, and a Ph.D. in mathematics at the University of Bonn in 1964.

Jensen was honored by the Association for Symbolic Logic as the first Gödel Lecturer in 1990.

[1] In 2015, the European Set Theory Society awarded him and John R. Steel the Hausdorff Medal for their paper "K without the measurable".

Jensen's better-known results include the: