Olongapo City National High School (OCNHS) was established in 1946, the time when Filipinos were at the height of rehabilitation from World War II.  It started  as the  Reservation High School  with  an  initial  enrolment  of  320  students  under the United  States  (US) Naval  Reservation Administration.  The growth and development of the school runs parallel with the growth and development of the city of Olongapo.  The school was later turned-over to the Republic of the Philippines by virtue  of  RP-US base agreement in 1954, and was renamed Olongapo High School.  By virtue of Executive Order number 336 issued by President Carlos P. Garcia the school was reconverted to a municipal school under the division of Zambales.   It later became a provincial high school in 1962. When Congressman Ramon Magsaysay worked for the approval of Republic Act 4645 converting Olongapo into a chartered city on June 1, 1966, the school was renamed Olongapo City High School. It became a national high school on September 2, 1972, carrying its present name.

Olongapo City National High School (OCNHS) is the pioneer high school in the city where the Subic Bay Metropolitan Authority (SBMA) Freeport Zone is established. It used to be the school where American and Amer-asian children study when the US Naval Base was in existence until November 1992. The community is a melting pot of families who came from all sectors of the country. The school is a contributor to the popularity of the SMBA because of the work volunteerism performed by the students and the men and women behind this school.

Olongapo City National High School is located in the Central part of Olongapo City along Rizal Avenue, corner 14th Street, East Tapinac with a total service area of 18,993 square meters. It is 2.43 kilometers away form the Department of Education (DepEd) Division Office, Olongapo City. Today the population of the school after 60 years has reached 7,500.