Monmouth College is a private Presbyterian liberal arts college in Monmouth, Illinois, United States. It enrolls 727 students in Bachelor of Arts and Bachelor of Science degree programs including a four-year nursing program and four-year electrical engineering and mechanical engineering programs.

Monmouth College was founded on April 18, 1853, by the Second Presbytery of Illinois of the Associate Reformed Presbyterian Church. Founded as Monmouth Academy, the school became Monmouth College after receiving a charter from the state legislature on September 3, 1856. The college remains affiliated with the Presbyterian Church (USA) and is a member of the Associated Colleges of the Midwest, a consortium of small, private liberal arts colleges. The college's motto "Lux" ("Light") appears on its seal.

The first president, David Wallace built two mission churches in Massachusetts before assuming the Monmouth presidency.

Founded on the eve of the American Civil War, the college immediately faced a crisis. The college's campus was still under construction while virtually the entire male student body left for military service. Two hundred and thirty-two students, faculty members, and trustees served in the Civil War. A quarter of them were wounded and one in eight was killed. Two were awarded the Medal of Honor, and Abner C. Harding, a college trustee who raised a regiment composed largely of Monmouth College students, was commissioned a brigadier general for his leadership in the defense of Fort Donelson in 1863. President Wallace, believing that the college "must educate, whether there be peace or war", kept classes in session for what was then a primarily female student body.

Monmouth was founded as a coeducational college where women and men had equal access to courses. When veterans returning to the college decided to form fraternities, a group of women was determined not to be outdone, and in 1867 established the first fraternity for women, known today as Pi Beta Phi. Three years later, another well-known women's fraternity, Kappa Kappa Gamma, was founded at Monmouth.

Monmouth College had gained national stature by 1911 as shown by its US government classification where 59 colleges and universities ranked higher and 244 ranked lower (out of a total of 345 top colleges).

World War II posed a crisis to the institution similar to that of the Civil War, as male students began enlisting in the service within a month of the Japanese attack on Pearl Harbor, and soon only a handful remained on campus. Through an arrangement with the U.S. Navy Department, the college survived by becoming a U.S. Naval Flight Preparatory School, and later offered a V-5 Navy Academic Refresher Unit program for officers. Courses were taught by Monmouth's liberal arts faculty. The Navy later adopted portions of Monmouth's curriculum for training programs nationwide. More than 2,000 Navy men went through Monmouth College, a number of whom would re-enroll at the college after the war funded by the G.I. Bill.

Monmouth's chemistry department gained national prominence in the 1950s when longtime professor William S. Haldeman was recognized with a major award by the American Chemical Society. The Steelman Report on Manpower for Research noted that Monmouth and four other small colleges—Hope, Juniata, St. Olaf and Oberlin—together had "produced more candidates for the doctor's degree in chemistry than Johns Hopkins, Fordham, Columbia, Tulane and Syracuse Universities combined."