Louis Nirenberg is a Canadian American mathematician, considered one of the outstanding analysts of the 20th century. He has made fundamental contributions to linear and nonlinear partial differential equations (PDEs) and their application to complex analysis and geometry. His contributions include the Gagliardo Nirenberg interpolation inequality, which is important in the solution of the elliptic partial differential equations that arise in many areas of mathematics, and the formalization of the bounded mean oscillation known as John Nirenberg space, which is used to study the behavior of both elastic materials and games of chance known as martingales. He was born on February 28, 1925 Hamilton, Canada. He has received many honours and awards, including the Bôcher Memorial Prize (1959), the Jeffery–Williams Prize (1987), the Steele Prize (1994 and 2014), the National Medal of Science (1995), and was the inaugural recipient of both the Crafoord Prize (1982, shared with Vladimir Arnold) and the Chern Medal (2010). In 2015 he was awarded the Abel Prize along with John Nash. He is a fellow of the American Mathematical Society.