Marian University is a private Catholic university in Fond du Lac, Wisconsin, United States. It was founded in 1936 by the Congregation of Sisters of Saint Agnes, which continues to sponsor the university today.

Marian University has an enrollment of approximately 2,000 undergraduate and graduate students. Seventy-one percent of students are women. Ninety-four percent of students receive financial aid. Approximately 32% of undergraduate students live on campus.

Marian University opened as Marian College of Fond du Lac, Wisconsin on September 8, 1936, with 17 full-time and 25 part-time students and eight faculty. The Congregation of Sisters of St. Agnes founded the college in response to a Wisconsin Department of Instruction decision that nuns were not allowed to teach in public schools while wearing their religious habits.

Marian became accredited to offer an undergraduate degree in elementary education in 1941. The first graduating class in August 1941 had eight nun graduates. The first lay students graduated in 1942. Although Marian was founded as a women's college, the male superintendent of Fond du Lac schools attended art and music classes with his wife in 1940. Marian had 86 full-time and 145 part-time students in 1950 who attended classes in a convent next to St. Agnes Hospital. Increasing enrollment caused the college to move to its current 100 acres (40 ha) campus on Fond du Lac's east side in the mid-1960s. The college became co-educational in 1970.

The school became accredited by the North Central Association for a Master of Arts program in 1987.

On May 1, 2008, Marian College of Fond du Lac changed its name to Marian University to reflect an expansion of its programs and classes and to position the institution for continued growth.

In 2021, the college was sanctioned by the American Association of University Professors "for infringement of governance standards".

Marian University consists of two colleges, namely the College of the Professions and the College of Arts, Sciences and Letters.