Ignatius L. Donnelly
 Ignatius Loyola Donnelly (November 3 1831 – January 1 1901) was a U.S. Congressman populist writer and amateur scientist known primarily now for his theories concerning Atlantis Catastrophism (especially the idea of an ancient impact event affecting ancient civilizations) and Shakespearean authorship which many modern historians consider to be pseudoscience and pseudohistory. Brother to Eleanor C.