Isabelle Case La Follette (April 21, 1859 – August 18, 1931), known as Belle Case, was a women's suffrage, peace, and civil rights activist in Wisconsin, United States. She worked with the Woman's Peace Party during World War I. At the time of her death in 1931, The New York Times called her "probably the least known yet most influential of all American women who have had to do with public affairs in this country." She was the wife and helpmate of Robert "Fighting Bob" La Follette—a prominent Progressive Republican politician both in Wisconsin and on the national scene—and as co-editor with her husband of La Follette's Weekly Magazine.