he Municipality of Banayoyo is one of the 34 municipalities of Ilocos Sur in Region I.  It lies within the latitude 17 11' to 17 15' and longitude 120 26' to 120 34'.  It is bounded on the south by Bucong River, also called "Carayan a Bassit", on the west by a small canal called "Calip", on the east by Cabcaburao Hills and on the north by Bay-asan Hills.  Municipalities adjacent to the town are: on the east by Lidlidda, on the south by Candon, on the west by Santiago and on the north by Burgos.   It has 14 barangays bisected by Naguimba River at the center.

Banayoyo is approximately 3.4 kilometers east of Manila North Road.  It is 57 kilometers south of Vigan, the Provincial Capitol town; 8.5 kilometers northeast of Candon town proper; 85.5 kilometers from San Fernando City, La Union, the Regional Capital; 145.5 kilometers from Baguio City and 352 kilometers from Manila.  The municipality can be reached by jeepneys going to Lidlidda and San Emilio or tricycles from Candon.