William Thomas Walsh was an American Catholic historian, author, educator, and violinist. He is best known for popular biographies of Spanish Catholic historical figures and for his 1947 book Our Lady of Fatima, which significantly increased awareness of the Fatima apparitions among American Catholics. He received the Laetare Medal from the University of Notre Dame in 1941. Walsh wrote from a strongly Catholic perspective; his interpretations of Spanish history, particularly regarding the Inquisition and the expulsion of the Jews, have been both praised in Catholic circles and criticized by some historians for alleged antisemitic bias.

Characters of the Inquisition
1940
ISBN 9780895553263
Our Lady of Fatima
1947
ISBN 9780385028691
Isabella Of Spain: The Last Crusader
1963
ISBN 9780895553201