Bishop Denis J. O'Connell High School is a Roman Catholic college preparatory school founded in 1957 in Arlington County, Virginia. It was established by the Diocese of Richmond, but it has been under the direction of the Diocese of Arlington since 1974. The school is named for Bishop Denis J. O'Connell, Bishop of Richmond from 1912 to 1926.

The Diocese of Arlington is a Latin diocese of the Catholic Church in Northern Virginia in the United States. It is a suffragan diocese in the ecclesiastical province of the Archdiocese of Baltimore. The Cathedral of St. Thomas More is the mother church of the diocese.