William "Velvel" Morton Kahan (born June 5, 1933) is a Canadian mathematician and computer scientist, who is a professor emeritus at University of California, Berkeley.

Kahan is now emeritus professor of mathematics and of electrical engineering and computer sciences (EECS) at the University of California, Berkeley.

He coined the term "Table-maker's dilemma" for the unknown cost of correctly rounding transcendental functions to some preassigned number of digits.

[6][7][8] When Hewlett-Packard (HP) introduced the original HP-35 pocket scientific calculator, its numerical accuracy in evaluating transcendental functions for some arguments was not optimal.

[9][10] He also contributed substantially to the design of the algorithms in the HP Voyager series and wrote part of their intermediate and advanced manuals.