Saint Louis School is a historic Catholic college preparatory school for boys located in the neighborhood of St. Louis Heights in Honolulu, Hawaii. It was founded in 1846 to serve Catholics in the former Kingdom of Hawaii. Located within the Diocese of Honolulu, it is affiliated with the Society of Mary, a religious order of brothers and priests called the Marianists who also administer Chaminade University of Honolulu, formerly the college section of Saint Louis School. It is located near Sacred Hearts Academy, a girls' school founded by the Congregation of the Sacred Hearts of Jesus and Mary, and both schools hold joint programs such as cultural festivals and the JROTC.

Saint Louis School was originally located in the ʻĀhuimanu area of windward Oʻahu as the College of ʻĀhuimanu, founded in 1846 by the Fathers of the Society of Mary. In 1881, the school was relocated to Beretania Street, in downtown Honolulu, adjacent to Washington Place, the home of Liliuokalani, who was Queen of Hawaii from 1891 to 1893. When the school moved to downtown Honolulu, it was called the College of Saint Louis, named after the patron saint of Louis Maigret, Bishop of Honolulu. In 1883, the school moved again for a third time to Kamakela (known today as College Walk), on the bank of the Nuʻuanu Stream, near Chinatown, Honolulu. This remained the campus until the 1920s.

The high school and college sections eventually split up and the emblem for Saint Louis College can be seen above the door of the administration building of Chaminade University on the Chaminade/Saint Louis campus. Marianists assumed control of the school and determined a need to expand facilities to serve the burgeoning Hawaiian Catholic population, who included many Filipino immigrants. Because of the Marianist core mission to educate regardless of ethnic, religious, or fiscal means, the Order purchased land in Kalaepōhaku, a hillside division of Honolulu's Kaimuki community, to enable the school to better serve Hawaii. Kalaepōhaku opened in September 1928 as Saint Louis School.

In the years following World War II, Saint Louis School re-evaluated its mission. Beginning in 1949, it dropped the lower grade levels one at a time, concentrating on a curriculum as a high school serving grades 9 through 12.

In 1980, it reinstated grades 7 and 8. In 1990, grade 6 was reinstated. The school created a middle school consisting of grades 6 through 8, operating independently within Saint Louis School. Grade 5 was reinstated and added to the middle school. In 2015 Saint Louis School announced its plans to expand again to become a K-12 school for the 2016–17 school year. That same year, it hired former pop singer Glenn Medeiros as its president. An article from nonprofit news organization Honolulu Civil Beat focused on allegations of mismanagement under Medeiros’ leadership, including retaliation against staff and nepotism for allowing his wife to run a nail salon at the school. However, members of the board have refuted these claims, while acknowledging there had been some challenges.

Saint Louis School is fully accredited by the Western Catholic Education Association (WCEA) and the Western Association of Schools and Colleges (WASC). It offers three distinct curricula.

Listed alphabetically by last name (year of graduation):

Government