A titular bishop in various churches is a bishop who is not in charge of a diocese. By definition a bishop is an "overseer" of a community of the faithful, so when a priest is ordained a bishop the tradition of the Roman Catholic and Orthodox churches is that he be ordained for a specific place. As there are more bishops than there are dioceses, a bishop who will not functionally head a diocese or archdiocese (they are destined to be appointed, e.g., an auxiliary bishop, a papal diplomat, an official of the Roman Curia, etc., or have retired from one of those) is given title of bishop. This is often (though not always) to a Titular see, i.e. a diocese that no longer functionally exists.

In the Roman Catholic Church, a titular bishop is a bishop who is not in charge of a diocese (Canon 376). Examples of bishops belonging to this category are coadjutor bishops, auxiliary bishops, bishops emeriti, vicars apostolic, nuncios, superiors of departments in the Roman Curia, and cardinal bishops of suburbicarian dioceses (since they are not in charge of the suburbicarian dioceses). Most titular bishops hold the title to a titular see. Assigning titular sees serves two purposes. Since part of being a bishop means being the head of a Church, titular sees serve that purpose for bishops without a diocese. At the same time, the office of titular bishop memorializes ancient Churches, most of which were suppressed because they fell into the hands of non-Christian conquerors. For this reason the former terminology was not "titular bishop" but "bishop in infidel regions" (in partibus infidelium). In recent times the names of titular sees are drawn also in numerous cases from those of former dioceses which were absorbed into other dioceses or expanded and hence moved to larger towns and cities.

Athanasius Schneider (born Anton Schneider on 7 April 1961) is a Roman Catholic bishop who is the auxiliary bishop of Astana, Kazakhstan and titular bishop of Celerina. He is a member of the Canons Regular of the Holy Cross of Coimbra.

Anton Schneider was born in Tokmok, Kirghiz SSR in the Soviet Union. In 1973, shortly after making his first Holy Communion by the hand of Bl. Oleksa Zaryckyj, priest and martyr, he left with his family for Germany. When he joined the Canons Regular of the Holy Cross of Coimbra, a Catholic religious order, he was given the religious name Athanasius. He was ordained a priest on 25 March 1990. Starting in 1999, he taught Patristics at Mary, Mother of the Church Seminary in Karaganda. On 2 June 2006 he was consecrated Bishop at the Altar of the Chair of Saint Peter in the Vatican by Angelo Cardinal Sodano. In 2011 he was transferred to the position of auxiliary bishop in the Archdiocese of Astana. Bishop Athanasius Schneider is the General Secretary of the Bishops' Conference of Kazakhstan.

Mar Bosco Puthur മാര്‍ ബോസ്കോ പുത്തൂര്‍ (b. 28 May 1946, Parappur, Kerala, India) is a Syro Malabar Catholic Bishop. He is the Curia Bishop of the Archdiocese of Ernakulam-Angamaly. Previously, he has served as Rector of St. Joseph's Pontifical Seminary, Mangalapuzha. He was also a Monsignor of the Syro-Malabar Catholic Archdiocese of Thrissur. Following the sudden death of Mar Varkey Vithayathil, he has also served as the Administrator of the Major Archdiocese of Ernakulam-Angamaly and of the Syro-Malabar Church.