William Caspar Graustein (15 November 1888 – 22 January 1941) was an American mathematician.

In 1921, he married Mary Curtis Graustein (1884—1972), who was the first American woman to earn a mathematics Ph.D. (1917) from Radcliffe College.

[2] He died in an automobile accident, at the age of 52.

At the time, Graustein was professor of mathematics and assistant dean at Harvard.

This article about an American mathematician is a stub.