The Diocese of Alexandria in Louisiana is a Latin Church ecclesiastical territory, or diocese, of the Catholic Church in central Louisiana in the United States. It is a suffragan diocese in the ecclesiastical province of the metropolitan Archdiocese of New Orleans.

The Archdiocese of New Orleans is a Latin Church ecclesiastical division of the Catholic Church spanning Jefferson, Orleans, Plaquemines, St. Bernard, St. Charles, St. John the Baptist, St. Tammany, and Washington civil parishes of southeastern Louisiana. It is the second to the Archdiocese of Baltimore in age among the present dioceses in the United States, having been elevated to the rank of diocese on April 25, 1793, during Spanish colonial rule.