Wilhelmus Anthonius Josephus Luxemburg (born 11 April 1929, in Delft, Netherlands) is Professor of Mathematics, Emeritus at the California Institute of Technology.
He received his B.A. from the University of Leiden in 1950; his M.A., in 1953; his Ph.D., from the Delft Institute of Technology, in 1955. He was Assistant Professor at Caltech during 1958-60; Associate Professor, during 1960-62; Professor, during 1962-2000; Professor Emeritus, from 2000. He was the Executive Officer for Mathematics during 1970-85. In 2012 he became a fellow of the American Mathematical Society. Luxemburg became a corresponding member of the Royal Netherlands Academy of Arts and Sciences in 1974.
Joseph Dauben (1995) attributes the ultrapower construction of the hyperreal numbers to Luxemburg in 1962. Such a construction was originally introduced by Edwin Hewitt in 1948, and popularized by Luxemburg in the 1960s.