Punahou School (known as Oahu College until 1934) is a private, co-educational, college preparatory school for both boys and girls in Honolulu, Hawaii. More than 3,700 students attend the school from kindergarten through 12th grade. The school was established by Protestant missionaries in 1841.

From 1853 to 1934, the school was known as Oahu College.

Punahou has educated members of the Hawaiian royal family, but is not to be confused with the Royal School.

During World War II, the U.S. Army Corps of Engineers commandeered much of the Punahou campus. Castle Hall, formerly the girls' dormitory when Punahou had boarding students, was used as a command center, buildings were connected with tunnels, athletic fields were used as parking lots, and the library was cleared to become sleeping quarters and an officer's mess. The cereus hedge on the campus lava rock wall was topped with barbed wire. Punahou students volunteered in hospitals and raised enough in war bonds to purchase two bombers and a fighter (among other airplanes), which were named after alumni who had fallen in service.

In the 1970s, Punahou's upper field and gymnasium were used for the Superstars nationally televised athletic competitions.

On August 7, 1972, the campus was added to the National Register of Historic Places listings in Oahu.

Many traditional events take place on campus. On the first Friday and Saturday of each February, the junior class hosts the Punahou Carnival. Proceeds from the carnival contribute to the Financial Aid program. The event is an entertainment highlight each year in Honolulu.

The Holoku Pageant is an annual celebration of the Hawaiian culture and arts. Students perform Hawaiian dances in traditional costumes, from the lovely hula to the intimidating haka.

The annual Sustainability Fair began in 2007 and included on-campus conservation challenges and off-campus coastline preservation. On Rice Field, classes set up canopies to showcase sustainable undertakings and projects, often including local produce sales and informational handouts.

To celebrate the school's homecoming, students, faculty, and teachers surround a 20-foot letter P, and ignite it at dusk. This event, the "Flaming P", is preceded by a spirit week, where students dress and parade creatively.

Seniors write and perform a Variety Show. This play involves most of the class, over 300 students. Seniors also have prom at the Sheraton Waikiki Hotel, Skip Day at the Kikila Estate and Pounders Beach, and senior lunch. With each student attired in either a blue blazer or a formal white Hawaiian dress, senior year ends with baccalaureate ceremonies at Central Union Church, and commencement at Stan Sheriff Center (since 2018).

Graduates who started Punahou in kindergarten are members of the Thirteen Plus Club.

In June, the school hosts an Alumni Luau on campus that the newly graduated class can enjoy with other alumni. The annual luau also functions as a major fundraising event for the school.

Throughout most of the school's history, elementary schoolchildren have been allowed to attend in bare feet. Aloha shirts were once restricted to Fridays, but dress codes were relaxed considerably during the 1970s.

G-Term is an effort for students to explore extracurricular opportunities over the week after students return from winter break. Students can choose from on- and off-island classes.

All schools in Honolulu city (public and private) have an urban residential location. Nearby buildings include apartment buildings, private houses, a retirement home, a Catholic school (Maryknoll School), several small churches, and two hospitals.

Punahou shares the entrance to Manoa Valley with the University of Hawaii main campus and a few other schools such as Mid-Pacific Institute.

Punahou students are a few minutes away from the trail to Manoa Falls, the beaches at Ala Moana and Waikiki, downtown Honolulu, Lyon Arboretum, and the National Memorial Cemetery of the Pacific.

Punahou's location provides many opportunities for off-campus learning: field trip destinations for middle school students have included the Bishop Museum, Waikiki Aquarium, Waikiki Shell, Waikiki Natatorium War Memorial, Kawaiahaʻo Church, Sea Life Park, USS Arizona Memorial, Valley of the Temples Memorial Park, Fort Ruger at Diamond Head, Hanauma Bay, Honolulu Museum of Art, Honolulu Zoo, Iolani Palace, Hawaii State Capitol, and the beaches on Oahu's North Shore. Clubs and classes often organize trips to neighboring islands, especially to Hawaii Volcanoes National Park and the Kohala Coast on the Big Island.

Tuition was $30,480 for the 2023–24 school year, not including student activity fees. Tuition does not cover the entire cost of educating a student, and the school's endowment makes up the difference. Punahou reported its endowment at $239 million in 2014. Although these figures are high among mainland U.S. private schools, Honolulu's Iolani School has a comparable endowment (twice the endowment per pupil), and Kamehameha Schools has a $5 to $9 billion endowment (30 times the endowment per pupil) with a larger physical plant. Maui has Seabury Hall, which has twice the endowment per pupil.

In the class of 2015, three graduates went to Harvard, three to Princeton, and two to Yale, with 22 total at Ivy League schools. Seven attended Swarthmore, Wellesley, Amherst, Tufts, or Vassar. Four attended Stanford, two Berkeley, four Massachusetts Institute of Technology, 16 Boston University, and 12 New York University, with 23 total at University Athletic Association schools. Students in that class also chose Texas Christian, Notre Dame, Vanderbilt, Villanova, Rensselaer Polytechnic, Rochester Institute of Technology, Michigan, Northeastern, Boston College, Olin Engineering, Norwich Military College, NYU Shanghai, Erasmus/Rotterdam, Yonsei/S. Korea, Waseda/Japan, and Edinburgh/UK. Six were selected for study and training at US military academies. Schools throughout California, Washington, Oregon, Colorado, Utah, Arizona, and Nevada are also popular among graduates, and many students choose to attend local schools like the University of Hawaii and Chaminade.

The class of 2012 had 30 of Hawaii's 70 National Merit Semifinalists. The class of 2013 had 20 semifinalists, and five of the state's ten National Merit Scholars.

Punahou's 33 Presidential Scholars were graduates of the classes of '64, '66, '70, '71, '75, '78 (two), '79, '82, '84 (two members), '85, '86 (two), '91, '92 (two), '93, '95, '96, '98, '01, '02, '04 (three), '05, '06, '08, '11, '16 (two), '17, and '21.

In 2006, it was ranked the greenest school in America. In 2017, Punahou's sports program was ranked second nationally in the MaxPreps Cup standings.

Punahou's student body is diverse, with student selection based on both academic and non-academic considerations. The school is a founding member of the Mastery Transcript Consortium, and uses a competency-based learning framework in some courses.

A recent study of the class of 1979 showed that 15 had a PhD, 22 had an MD, 39 had a JD, 18 had the MBA, 10 had the DDS, DMD, DVM, or ND (about one quarter of the class reaching terminal degrees). 4 were officers in the US armed services. 12 had degrees from Harvard, Yale, or Princeton, 14 from Stanford, 17 from UC Berkeley, and 26 total from Ivy League schools.

About 5,000 faculty, students, and staff work in 44 buildings on 76 acres. The Robert Thurston Memorial Chapel on campus was building designed and built in 1966 by architect Vladimir Ossipoff and feature textile screens made by local artist Ruthadell Anderson. The school is built over a natural spring. Thurston Chapel's wall meets at a pond formed by the spring and features a low hung stained glass.

Before plans were made for a new middle school complex, America Online founder and alumnus Steve Case ('76) donated $10 million. This led to construction of a new middle school for grades six through eight, Case Middle School, named for Case's parents. The project earned a Leadership in Energy and Environmental Design Gold certification and a Project of the Year award in Hawaiian Electric Company's Energy Efficiency Awards.

Case Middle School consists of nine buildings with a total cost of roughly $50 million, made possible solely through donations.

In late 2010 a new five-building indoor/outdoor section of campus opened for Punahou's youngest students. It was constructed and operated with sustainable living as a principal goal, and the curriculum has a focus on sustainability. With solar energy, efficient landscaping, rain catchment and ecofriendly materials, the complex received a platinum rating from the U.S. Green Building Council.

Teachers are encouraged to personalize their classroom spaces, and each of the 12 rooms has its own outdoor area that is one-third the size of the interior space to which it is attached.

The total cost was $26 million. Individual buildings are named the Mountain House, Forest House, and City House, and historic Wilcox Hall retains its traditional name. Board of Trustees member and eBay founder Pierre Omidyar ('84) donated $6 million to the project.

Punahou's athletics program is the most successful in Hawaii. It has won more state championships than any other high school in the nation. In 2008 and in 2009, Sports Illustrated ranked Punahou's sports program the best in the country.

Punahou football plays the second half of its season at the Aloha Stadium (where the Pro Bowl and Aloha Bowl were played). In fall 2014, the varsity football team ranked as high as 15th in the nation.

Athletic facilities include the Olympic-size Waterhouse Pool, a football field, a baseball diamond, two softball diamonds, and an eight-lane track. The school also has a fieldhouse for competitive athletics, an open-air weightlifting facility, a gymnasium for physical education and intramural sports, and a tennis center with eight hard surface courts. Rocky Hill has been used as a live firing range for JROTC and competitive target sports. Air riflery uses an indoor firing range.

Students need two athletic credits to graduate, which is a total of four semesters. They can earn these credits through P.E. and ILH sports.

Students compete in 22 sports, including air riflery, baseball, basketball, bowling, canoe paddling, cross country, cheerleading, football, golf, gymnastics, judo, kayaking, riflery, sailing, soccer, softball, swimming and diving, tennis, track and field, volleyball, water polo, and wrestling. Punahou has approximately 120 sports teams. The school is a member of the Interscholastic League of Honolulu.

Punahou teams earned 20 championships in 2009–10, out of about 30 varsity it teams fielded.

State championships

Sea­son	Sport	Number of champ­ionships	Year
Fall	Football	2 + 12	2008, 2013 *State championship bowl instituted in 1973. Prior to 1973, Punahou had 19 ILH championships. As the OIA was founded in 1940, the ILH championships of 1909–1917, 1919–1920, and 1924 can be considered "state" or "island" championships. Punahou is 2–3 in the state bowl against OIA opponents.
	Volleyball, Girls	9	1973, 1993, 1996, 2000, 2003, 2004, 2011, 2012, 2014
	Cross Country, Boys	13	1965, 1978, 1981, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1996, 2019, 2021
	Cross Country, Girls	35	1973, 1974, 1978, 1979, 1981, 1982, 1983, 1984, 1985, 1986, 1988, 1991, 1992, 1995, 1996, 1997, 1999, 2000, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2021, 2022, 2023
	Air Riflery, Boys	7	2005, 2006, 2007, 2008, 2009, 2011, 2014
	Air Riflery, Girls	6	2001, 2002, 2005, 2008, 2011, 2016
Winter	Wrestling, Boys	8	1967, 1968, 2007, 2008, 2009, 2010, 2011, 2012
	Wrestling, Girls	3	2009, 2010, 2011
	Basketball, Boys	11	1970, 1974, 1975, 1979, 1980, 1981, 1990, 1999, 2008, 2012, 2018
	Basketball, Girls	11	1979, 1980, 1981, 1994, 1997, 1998, 2003, 2005, 2006, 2008, 2013
	Soccer, Boys	22	1976, 1977, 1982, 1983, 1985, 1986, 1989, 1990, 1991, 1992, 1994, 1995, 1996, 1998, 2006, 2007, 2010, 2011, 2015, 2016, 2017, 2019, 2020
	Soccer, Girls	13	1983, 1984, 1985, 1986, 1998, 2003, 2004, 2005, 2009, 2010, 2011, 2023, 2024
	Swimming, Boys	49	1958, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1997, 1999, 2001, 2007, 2008, 2010, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020
	Swimming, Girls	56	1958, 1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970, 1971, 1972, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1997, 1999, 2000, 2001, 2006, 2007, 2008, 2009, 2011, 2012, 2013, 2015, 2016, 2017, 2018, 2019, 2020, 2022, 2023, 2024
	Canoe Paddling, Boys	9	2002, 2012, 2014, 2015, 2016, 2017, 2020, 2022, 2023
	Canoe Paddling, Girls	7	2006, 2008, 2009, 2014, 2015, 2018, 2019, 2022
	Canoe Paddling, Mixed	6	2009, 2014, 2015, 2019, 2022, 2023
Spring	Golf, Boys	10	1970, 1995, 1996, 1997, 2008, 2010, 2011, 2013, 2014, 2015
	Golf, Girls	13	2007, 2008, 2009, 2010, 2011, 2013, 2014, 2015, 2016, 2017, 2018, 2022, 2024
	Volleyball, Boys	39	1972, 1973, 1974, 1975, 1976, 1977, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1992, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2004, 2005, 2007, 2009, 2010, 2011, 2013, 2014, 2015, 2017, 2018, 2019, 2022, 2023
	Water Polo, Girls	15	2004, 2005, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2017, 2018, 2019, 2022
	Tennis, Boys	51	1958, 1959, 1960, 1961, 1962, 1963, 1964, 1969, 1970, 1972, 1973, 1974, 1975, 1976, 1977, 1979, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2022, 2023, 2024
	Tennis, Girls	47	1959, 1960, 1961, 1962, 1963, 1964, 1965, 1966, 1967, 1968, 1969, 1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1981, 1983, 1984, 1985, 1986, 1988, 1989, 1990, 1991, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2017, 2018, 2019, 2022, 2023, 2024
	Judo, Boys	3	2006, 2008, 2009
	Judo, Girls	3	2009, 2010, 2011
	Track and Field, Boys	36	1959, 1960, 1961, 1962, 1965, 1967, 1968, 1969, 1970, 1972, 1973, 1974, 1975, 1977, 1978, 1979, 1980, 1984, 1988, 1989, 1990, 1993, 1995, 1996, 1997, 1998, 1999, 2001, 2002, 2007, 2008, 2010, 2011, 2017, 2018, 2019, 2022
	Track and Field, Girls	40	1967, 1968, 1969, 1970, 1972, 1977, 1978, 1979, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1996, 1997, 1998, 1999, 2000, 2001, 2004, 2005, 2006, 2007, 2009, 2010, 2011, 2012, 2013, 2018, 2019, 2022, 2023, 2024
	Softball	1	2013
	Baseball	14	1961, 1964, 1966, 1968, 1972, 1989, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2019
Total		539

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Punahou requires all students (K-12) to attend chapel once a week, where each homeroom is assigned its own seating and attendance is taken. In addition, students attend a mandatory weekly assembly to listen to announcements or watch student performances.

115801 Punahou is a minor planet named in the school's honor.

In April 2020, several former Punahou girls' basketball players filed a lawsuit over alleged abuse committed by their former coach Dwayne Yuen. Days later, the school disclosed additional sexual assault allegations dating back to the 1970s involving a former faculty member and baseball coach.

In January 2021, the school terminated the employment of a high school teacher based on allegations of sexual misconduct involving a former student. The teacher had been suspended from teaching and banned from campus since late November 2020 pending an internal investigation, which he did not cooperate with. The investigation found that the allegations were credible.

(Numerical claims are substantiated in the main article on alumni. * indicates the class year of an attendee who did not graduate with the class.)