Bagac, officially the Municipality of Bagac, is a 3rd class municipality in the province of Bataan, Philippines. It covers an area of 231.20 square kilometres (89.27 sq mi), making it the largest municipality in Bataan. However, according to the 2020 census, it has a population of 31,365 people, making it the least populated municipality in the province.

Bataan, officially the Province of Bataan, is a province in the Central Luzon region of the Philippines. Its capital is the city of Balanga while Mariveles is the largest town in the province. Occupying the entire Bataan Peninsula on Luzon, Bataan is bordered by the provinces of Zambales and Pampanga to the north. The peninsula faces the South China Sea to the west and Subic Bay to the north-west, and encloses Manila Bay to the east.