Thaddeus C. Radzilowski (4 February 1938 – 20 July 2018) was an American historian, scholar, author, and professor. He was born in Detroit, Michigan. He was co-founder of the Piast Institute, a national institute for Polish and Polish-American affairs. His work focused on Poland and other Central and Eastern European nations, including Russia.
Radzilowski taught widely in Europe and North America and published more than 100 monographs, edited collections, journal articles, book chapters and scholarly papers.
Radzilowski died in Detroit on 20 July 2018 at the age of 80.