Santiago is an independent component city located in southwestern part of Isabela in northern Luzon island of the Philippines. It is the gateway to the Cagayan Valley. According to the 2010 census, it has a population of 132,804 people.
Santiago is situated north of Metro Manila. The city sits on a vast area of predominantly flat and fertile land in the Cagayan Valley, surrounded by the Caraballo Mountains to the south, the Great Sierra Madre to the east and the Cordillera Mountain Range to the west.
Though often grouped under the province of Isabela for geographic convenience, Santiago City is administratively and legally independent from the province as stated in Section 25 of the LGC.