Santo Niño, officially the Municipality of Santo Niño, is a municipality in the province of South Cotabato, Philippines. According to the 2020 cens…Santo Niño, officially the Municipality of Santo Niño, is a municipality in the province of South Cotabato, Philippines. According to the 2020 census, it has a population of 39,796 people, making it the least populated municipality in the province.