William Henry O'Connell was an American cardinal of the Catholic Church. He served as Archbishop of Boston from 1907 until his death in 1944, and was made a cardinal in 1911.

The Archdiocese of Boston is a Latin Church ecclesiastical territory, or archdiocese, of the Catholic Church in eastern Massachusetts in the United States. Its mother church is the Cathedral of the Holy Cross in Boston. The archdiocese is the fourth largest in the United States. As of 2023, the archbishop of Boston is Cardinal Seán Patrick O'Malley.