Frederick Daniel Wilhelmsen (May 18, 1923 – May 21, 1996) was an American philosopher and professor in the Thomist tradition. He also helped found Christendom College and taught at the University of Dallas for many years. He was a founding editor of Triumph magazine. He also taught at Santa Clara University for many years. A student of Étienne Gilson, he taught epistemology and metaphysics in the era of renewed interest by intellectuals in the work of Thomas Aquinas. Wilhelmsen enjoyed a lively friendship and correspndence with Marshall McLuhan, who spent time at the University of Dallas in the 1970s.
Wilhelmsen's works include Man's Knowledge of Reality.