The Diocese of Worcester is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in central Massachusetts in the United States. The diocese consists of Worcester County. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of Boston. The patron saint of the diocese is Paul the Apostle.

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.