Johann Friedrich Pfaff
Johann Friedrich Pfaff (December 22, 1765- April 21 1825) was a German mathematician. He is noted for his work on partial differential equations of the first order (Pfaffian systems as they are now called) which became part of the theory of differential forms; and as Carl Friedrich Gauss's formal research supervisor.
He was born in Stuttgart, and became a student of Abraham Kaestner. He knew Gauss well, when they were both in Helmstedt in 1798. August Möbius was later a student of his.
See also: Pfaffian.