Louis Joel Mordell (28 January 1888 – 12 March 1972) was an American-born British mathematician, known for his research in number theory.

He brought in Reinhold Baer, G. Billing, Paul Erdős, Chao Ko, Kurt Mahler, and Beniamino Segre.

A. Todd, Patrick du Val, Harold Davenport and Laurence Chisholm Young, and invited distinguished visitors.

[6] While visiting the University of Calgary, the elderly Mordell attended the Number Theory seminars and would frequently fall asleep during them.

According to a story by number theorist Richard K. Guy, the department head at the time, after Mordell had fallen asleep, someone in the audience asked "Isn't that Stickelberger's theorem?"