William David O'Brien (August 3, 1878 – February 19, 1962) was an American prelate of the Roman Catholic Church.
[3] He received his episcopal consecration on the following April 25 from Cardinal Mundelein, with Bishops Joseph Patrick Lynch and Bernard James Sheil, at Holy Name Cathedral.
[3] As an auxiliary bishop, he continued to serve as president of the Extension Society and pastor of St. John's Church, both offices which he held until his death.
During the playing of the Giovinezza, the Italian Fascist anthem, O'Brien gave a roman salute, another trademark of fascism.
[1] On November 18, 1953, O'Brien was elevated to the rank of Titular Archbishop of Calynda by Pope Pius XII.
[7] In his later years, he relinquished the editorship of the Extension Magazine and delegated many of his administrative duties, but still closely following the society's activities and frequently visiting its headquarters.