The Roman Catholic Diocese of Banja Luka (Serbian, Croatian: Banjalučka biskupija, Lat:Dioecesis Bania Lucensisis) a diocese of the Latin Rite of the Roman Catholic Church in western Bosnia. The diocese is centred in the city of Banja Luka, Bosnia and Herzegovina. Erected on July 5, 1881, the diocese is a suffragan of the Archdiocese of Vrhbosna, as the Diocese of Banjaluka.