Stanisław Marcin Ulam (1909 - 1984) Polish mathematician, participant in the Manhattan Project at Los Alamos, perhaps best-known for Ulam's spiral, the Ulam numbers and the Borsuk-Ulam theorem. The Collatz problem is occasionally referred to as Ulam's problem.

Born in Lwów to Jewish parents and educated in mathematics by Stefan Banach, Ulam went to the United States more than a year prior to the Nazi invasion of Poland. Although Ulam restated many ideas about the mathematics of the hydrogen bomb that had already been given by other Manhattan Project participants and much of the credit went to Edward Teller, the physicist Hans Bethe considered Ulam to be the true father of the H-bomb. After World War II, Ulam began teaching at the University of Colorado and shifted his focus to pure mathematics, but continued research at the Los Alamos National Laboratory.