The Municipality of Mahayag is located in the north-central region of Zamboanga Peninsula. It is approximately centered at geographical coordinates 8º09’7.0” North Latitude and 123º25’39.6” East Longitude. The Municipal Hall building is located at coordinates 8º07’50.7” North Latitude and 123º26’9.6” East Longitude based on a hand-held Garmin Global Positioning System (GPS) readings. Mahayag is bounded to the north by the Municipality of Sergio Osmeña, Sr.; the western border is bounded by the Municipality of Dumingag while the eastern side by the Municipality of Josefina. The Municipalities of Ramon Magsaysay and Aurora bound the south and southeastern sections, respectively. The commercial hub and the seat of the local government are located about 50 kilometers land distance northeast of Pagadian City. It is readily accessible to any form of land vehicles through the Pagadian-Labangan-Molave-Sergio Osmena National Highway.
Mahayag has a total land area covering 21,739.48 hectares representing 4.59 percent of Zamboanga del Sur’s total land area. Its land cover is further subdivided into nine (29) barangays and one (1) barangay (Poblacion) is the urban center considered as the growth center of the town.
Mahayag is typified by flat to gently sloping terrain on the southern and central sections and moderate to very steep sloping topography towards the north and northeast. All lowland barangays planted with palay and corns were classified as generally flat to gently sloping terrain. Barangays Tuboran, Diwan, San Vicente, Balanan, Bag-ongDalaguete, Delusom, Panagaan and portions of Upper SalugDaku, Kaanagayan, Boniao and Manguiles were classified as moderately sloping while Guripan, Paraiso, Pedagan, Malubo, Tulan were classified as strongly sloping or mountainous area.