William Fogg Osgood (March 10, 1864 – July 22, 1943) was an American mathematician.

The works of Osgood dealt with complex analysis, in particular conformal mapping and uniformization of analytic functions, and calculus of variations.

He was invited by Felix Klein to write an article on complex analysis in the Enzyklopädie der mathematischen Wissenschaften, which was later expanded in the book Lehrbuch der Funktionentheorie.

[3] Besides his research on analysis, Osgood was also interested in mathematical physics and wrote on the theory of the gyroscope.

[7] William Fogg Osgood died at his home in Belmont, Massachusetts on July 22, 1943.