Brunswick School is an all-boys college-preparatory private day school located in Greenwich, Connecticut, United States. It includes pre-kindergarten, a Lower School (grades 1–4), a Middle School (grades 5–8), and a high school, or, as it is called within the Brunswick Community, Upper School (grades 9–12).
The school's mascot is the Bruin, and its colors are brown, white, and gold.
The present Headmaster and Head of the Upper School is Thomas Philip. The present Lower and Middle School Heads are Kathleen Signer and Sarah Burdett, respectively.
The school motto is "Courage, Honor, Truth." The school proverb is "With All Thy Getting, Get Understanding."
Brunswick School was founded in 1902 by George B. Carmichael, a teacher at the nearby Greenwich Academy. The school is a college preparatory day school serving approximately 930 boys in grades pre-kindergarten through 12.
The school is made up of three different campuses. The Upper School campus is located on Maher Avenue in Greenwich. The Upper School English annex and pre-school building is located on North Maple Avenue, a short walk away from the Upper School. The bucolic Edwards Campus (named after former headmaster Duncan Edwards, II) is located about 15 minutes away from the Maher Avenue campus on King Street. Edwards Campus is made up of both the Middle School and Lower School buildings, as well as the Burke Fieldhouse (basketball, wrestling, tennis, and the Cosby Weight Room) and Sampson Fieldhouse (which houses the Dann O'Neil Gym, the Stephens Squash Courts, and Hartong Rink). A new turf field (Cosby Field) is the home to the varsity football, soccer, and lacrosse teams.They just built a newer turf behind the Middle School, which is resting upon their new pool. Additionally, Brunswick recently invested in a boat house located on River Road, just a twenty-minute drive from the Upper School campus. 
Coordination with Greenwich Academy
Brunswick's sister school is Greenwich Academy, which is located two blocks from Brunswick's Upper School campus. The two schools share classes with each other during Upper School, and students are able to choose courses from a combined course catalogue, with the exception of mathematics courses and ninth grade English, which remain separate. The connection between ""Greenwich Academy"" and Brunswick dates back to the school's founding. The founder of Brunswick had been previously employed as a teacher at Greenwich Academy, which was then a co-educational secondary school. After the founding of Brunswick, Greenwich Academy began admitting girls alone, directing boys to apply to Brunswick School.
- Akin Akingbala, former basketball player for Clemson University and the Boston Celtics
- Hayward Alker, international relations scholar
- Neil Burger, film director
- Peter Corroon, former mayor of Salt Lake County, Utah
- Peter Fonda, actor
- Pete Francis Heimbold, former member of the band Dispatch
- Matthew Heineman, Oscar-nominated filmmaker
- Justin Henry, actor
- Chris Jenkins (sound engineer), Oscar-winning sound engineer
- Hugh Jessiman, hockey player
- Rod Lurie, Film director
- Mitch Marrow, American football player
- Justin McAuliffe, businessman and member of the Hilton family
- Kevin Shattenkirk, hockey player
- Bill Simmons, sports columnist
- Christopher Tsai, investment manager and art collector
- Cameron Winklevoss, Olympic rower and social networking pioneer
- Tyler Winklevoss, Olympic rower and social networking pioneer
- Atta, John R. Van (2001). A place for boys : Brunswick School and the building of young men. Greenwich, Conn.: The School. ISBN 097116150X.
- "Archived copy". Archived from the original on 2009-02-21. Retrieved 2009-02-27.
- Brunswick School (2014). "Course Catalogue 2014-2015". Brunswick School. pp. 8, 28. Retrieved 2014-05-23.
- Greenwich Academy. "Greenwich Academy: History". Greenwich Academy. Retrieved 2014-05-23.