John Joseph Frederick Otto Zardetti was a Swiss prelate of the Roman Catholic Church. He first served as the first bishop of the new Diocese of Saint Cloud in Minnesota in the United States from 1889 to 1894. Zardetti then served as Archbishop of the Archdiocese of Bucharest in what is today Romania from 1894 to 1895. After resigning as archbishop, Zardetti briefly, but influentially served in the Roman Curia with the title of titular archbishop of Mocissus.

The Diocese of Saint Cloud is a Latin Church diocese of the Catholic Church in central Minnesota in the United States. It is a suffragan diocese of the metropolitan Archdiocese of Saint Paul and Minneapolis.