The Roman Catholic Diocese of Malacca Johore (Latin: Dioecesis Melakana-Giohorana) is a diocese of the Latin Church of the Catholic Church in the Ecclesiastical province of Kuala Lumpur in Malaysia. It is located in southern region of Peninsular Malaysia, administering Melaka and Johor states. The mother church is the Cathedral of the Sacred Heart of Jesus, in Johor Bahru, Johor(e); there is also a former Cathedral, now Church of St. Peter, in Melaka.