In the Roman Catholic Church, a Coadjutor Bishop or a Coadjutor Archbishop is a bishop or archbishop that has been appointed by the Pope to assist a diocesan bishop or archbishop with his diocese. Unlike auxiliary bishops, coadjutors are given the automatic right of succession to the episcopal see, meaning that when the ordinary they are assisting dies, retires, resigns, or is reassigned, the coadjutor automatically becomes the next leader of the diocese.

In modern church practice, this is usually done in cases where a diocesan bishop feels that he will not be able to continue much longer for health reasons, or because he is nearing retirement age. In these cases the Pope will sometimes assign a coadjutor to the diocese in question in order to give the new Bishop time to become familiar with the diocese that he will eventually take over. An example of this occurred in 1994 when Archbishop Jerome Hanus was named Coadjutor Archbishop of Dubuque as Archbishop Daniel Kucera was planning to retire. In 1995, Archbishop Kucera retired, and Hanus automatically became the next Archbishop of Dubuque.

At times, the appointment of a coadjutor is used to discreetly remove a diocesan bishop who has become involved in scandal or other problems and replace him with another man. An example of this occurred in Dubuque in the 1940's, when then Archbishop Beckman involved the archdiocese in what turned out to be a dubious mining scheme. When the scheme fell apart and the man behind the scam was arrested, the fallout resulted in serious financial problems for Archbishop Beckman and the archdiocese. Because of all Beckman's problems, Bishop Henry Rohlman of Davenport, Iowa, was appointed Coadjutor Archbishop of Dubuque. While Beckman was allowed to retain the office of Archbishop, it was made clear to him by the Vatican that the actual power rested with Rohlman. Beckman soon retired and left Dubuque.