Mellen Woodman Haskell (March 17, 1863 – January 15, 1948) was an American mathematician, specializing in geometry, group theory, and applications of group theory to geometry.
After secondary education at Roxbury Latin School, he received in 1883 his bachelor's degree and in 1885 his M.A.
In 1890 he was hired by the University of California, Berkeley as an assistant professor.
In particular, he identified the angle with area of a hyperbolic sector, and showed its invariance under squeeze mapping.
Haskell was an Invited Speaker of the International Congress of Mathematicians in 1924 in Toronto and in 1928 in Bologna.