Thomas Joseph Osler (April 26, 1940 – March 26, 2023) was an American mathematician, national champion distance runner, and author.

[2][3] He completed his PhD at the Courant Institute of Mathematical Sciences of New York University,[4] in 1970.

[11] In 2009, the New Jersey Section of the Mathematical Association of America gave him their Distinguished Teaching Award.

[14][15] Osler won the 1965 Philadelphia Marathon, finishing the race in freezing-cold weather in a time of 2:34:07.

[19] He has been credited with helping to popularize the idea of walk breaks among US marathon runners.