Hale Freeman Trotter (30 May 1931 – 17 January 2022)[1][2] was a Canadian-American mathematician, known for the Lie–Trotter product formula,[3] the Steinhaus–Johnson–Trotter algorithm, and the Lang–Trotter conjecture.

The son of historian Reginald George Trotter, Hale Trotter studied at Queen's University in Kingston with bachelor's degree in 1952 and master's degree in 1953.

He received in 1956 his PhD from Princeton University under William Feller with thesis Convergence of semigroups of operators.

From 1962 to 1986 he was an associate director for Princeton University's data center.

Trotter described an infinite number of pretzel knots that are not invertible.