Lars Valter Hörmander
From the American Mathematical Society, November 29, 2012
[Lars] Hörmander was a powerful analyst who revolutionized the modern theory of partial differential equations. Among many other contributions, his theories of pseudodifferential operators and Fourier integral operators will have lasting value. . . . In addition to the Fields Medal, Hörmander also was awarded the Wolf Prize in 1988 and the Leroy P. Steele Prize for Mathematical Exposition in 2006 for his influential four-volume The Analysis of Linear Partial Differential Operators. The prize citation states that "In the history of mathematics one is hard-pressed to find any comparable 'expository' work that covers so much material, and with such depth and understanding, of such a broad area of mathematics."
Fields Medalist, 1962