Isabelle Case La Follette (April 21, 1859 – August 18, 1931) 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.

Isabelle Case was born on April 21, 1859, in Summit, Juneau County, Wisconsin, and grew up on her family's farm in Baraboo. Her parents were Unitarians of English and Scottish descent. She attended the University of Wisconsin–Madison from 1875 to 1879 and, upon graduation, taught high school in Spring Green and junior high school in Baraboo. One of her students in Baraboo was John Ringling, of whom she later wrote "... when John read a long account -- interrupted with giggles from the school -- of the side shows he and other boys had been giving every night, I lectured him and drew the moral that if John would put his mind on his lessons as he did on side shows, he might yet become a scholar. Fortunately the scolding had no effect."

In 1875, Belle Case left home for the University of Wisconsin-Madison, with the financial support of her farming parents. She excelled as a student, never missing a class or arriving late while at the university.

Even early in life, Belle did not shy away from protesting what she perceived as injustices, particularly those targeted at women. In regard to one of her speeches, local paper Madison Democrat wrote, "... she portrayed the vanity of many of us in trying to make an empty display and neglecting it for true stability and depth of sentiment." In another speech, "Children's Playthings," Belle conflated the convention of young girls playing with dolls with future expectations for womanhood, claiming these domestic "dreams" of girlhood would only lead to "impossible future happiness" and "dissatisfied, nervous, complaining [women]."

Her senior oration is perhaps her most memorable. "Learning to See" highlighted natural curiosity and the danger of forcing children to conform to convention. It won her the Lewis Prize for best essay or oration produced by the graduating class.

Belle Case La Follette later returned to the University of Wisconsin and in 1885 became the University of Wisconsin Law School's first female graduate.

Belle Case and Robert "Bob" La Follette developed an early friendship at University of Wisconsin, their love of reform and rural backgrounds providing common ground for a potential courtship. Belle, however, only wished their bond to remain "free from sentiment," at least until they had left college.

While Belle excelled in her studies, Bob became notorious for poor grades but a clear, charismatic intelligence. While Bob helped Belle in her own speech-giving, Belle assisted Bob in his school work and other written projects (Bob would later only barely graduate, John Bascom himself having to provide the final say-so.) Their companionship eventually did blossom into an engagement. Bob would later say that, "Mamma laughed when I proposed to her."