Frederick D. Wilhelmsen (1923 – 21 May 1996) was a distinguished Roman Catholic philosopher, noted, both as a professor and as a writer, for his explication and advancement of the Thomistic tradition. He also was a political commentator, assessing American politics and society from a traditionalist perspective and a political thinker, addressing what he perceived to be the failings of secular-liberal democracy. He principally was a professor at the University of Dallas from 1965 to his death in 1996. He also taught at the University of Santa Clara, the Al-Hikma University in Baghdad, the University of Navarra in Pamplona, Spain, and lectured and taught classes at many other universities.
He was a prolific writer. Besides the book publications listed below, he contributed articles to the following: America, The Angelus, The Commonweal, Faith & Reason, The Grail, The Intercollegiate Review, Modern Age, National Review, The Political Science Reviewer, Triumph, The University Bookman, and The Wanderer, among others.
He also was a founding editor of Triumph, a Roman Catholic monthly that sought the sacralization of American society.
In addition to assessing American politics and society, he was inspired by and extensively reflected upon Spanish politics and society. Alvaro d'Ors, a notable Spanish political philosopher, wrote that Wilhelmsen, an American from Detroit, was "the best interpreter of Spanish traditionalism, a body of political thought also known as Carlism, after King Charles V (Don Carlos)".