Marian High School (also known as Mishawaka Marian) is a Roman Catholic secondary school in Mishawaka, Indiana, in the United States, operated by the Roman Catholic Diocese of Fort Wayne-South Bend. Marian was a top 50 school in 2005 noted on the Catholic High School Honor Roll. Marian High School holds a First Class commission from the Indiana State Department of Education and has been accredited by the North Central Association since early 1996. Marian received a letter grade of "A" for the 2013–2014 school year from the state. This is the third year that Marian has received this award

Marian High School was founded in 1964 by the Sisters of St. Francis. It was a co-educational school with separation of classes by gender (later changed).

Marian offers 18 Advanced Placement Program (Advanced Placement) courses which are eligible for college credit. AP courses offered for the 2014–2015 school year include: AP English Language and Composition, AP English Literature and Composition, AP World History, AP U.S. Government and Politics, AP U.S. History, AP Micro Economics, AP Latin, AP Psychology, AP Calculus-AB, AP Calculus-BC, AP Statistics, AP Biology, AP Chemistry, AP Physics 1, AP Physics-C Mechanics, AP Physics-C Electricity and Magnetism, and AP Studio Art-2D. In addition, Marian offers ACP(Advanced College Project) classes through Indiana University South Bend and non-AP dual credit courses through Ivy Tech Community College. These include Biology, Chemistry, Physics, U.S. History, Cadet Teaching, English, and Calculus.

Marian is part of the Northern Indiana Conference. Their teams are named the Knights and the school colors are royal blue and silver. The following sports are offered at Marian:

Marian's band includes both pep and concert band, which compete annually in the ISSMA competitions. The band performs during athletic events, as well as holding both a Christmas and Spring concert annually. As of April 2015, the school does not have a marching band.

Marian has participated in Indiana High School Mock Trial Association since the 1994 school year. The first year of the program, a Marian team won the state championship.

• Kyle Bornheimer (Class of 1994): Actor
• Devin Cannady (Class of 2015): professional basketball player
• D. J. Fitzpatrick: Former professional football player
• Zander Horvath (Class of 2017): professional football player
• Jaden Ivey: professional basketball player
• Demetrius Jackson (Class of 2013): professional basketball player
• Bob Otolski: Former Marian High School Athletics Director and head football coach for the Illinois State Redbirds football team

• List of high schools in Indiana

• Marian High School website