 It occupies an area of 4,850 square kilometers extending from the boundary of Zamboanga del Norte on the north to Olutanga Island on the south, from the town of Tungawan on the west to the town Margosatubig on the east boundaries set by Pope John Paul II himself when he decreed the separation of this ecclesiastical territory from the Archdiocese of Zamboanga on December 24, 1979.The area described above comprises the Province of Zamboanga Sibugay.The terrain is generally hilly bounded by mountains on the north and the Sibuyan Bay on the south.