Jan Karel Lenstra (born 19 December 1947, in Zaandam) is a Dutch mathematician and operations researcher, known for his work on scheduling algorithms, local search, and the travelling salesman problem.
Lenstra received his Ph.D. from the University of Amsterdam in 1976, advised by Gijsbert de Leve. He then became a researcher at the Centrum Wiskunde & Informatica, where he remained until 1989. After taking positions at the Eindhoven University of Technology (where he became Dean of the Faculty of Mathematics and Computer Science) and the Georgia Institute of Technology, he returned to CWI as its director in 2003. He stepped down in 2011, and at that time became a CWI Fellow. He was editor-in-chief of Mathematics of Operations Research from 1993 to 1998, and is editor-in-chief of Operations Research Letters since 2002.
Lenstra became an INFORMS fellow in 2004. In 1997, he was awarded the EURO Gold Medal, the highest distinction within Operations Research in Europe. In 2011, he was made a knight of the Order of the Netherlands Lion, and the CWI organized a symposium in his honor.