The Magnum Crimen is a book about clericalism in Croatia from the end of nineteenth century until the end of the Second World War. The book, whose full title is Magnum crimen - pola vijeka klerikalizma u Hrvatskoj (The Great Crime - a half-century of clericalism in Croatia), was written by a former Catholic priest and professor and historian at Belgrade University, Viktor Novak (1889-1977). The book was first published in Zagreb in 1948. Immediately after the book was published, Vatican Curia placed this book on Index librorum prohibitorum and pronounced anathema against the author.