Ciudad Madero is a coastal city located on the Gulf of Mexico in the southeastern part of the Mexican state of Tamaulipas. Lying within the metropolitan area of Tampico, it is the seventh most populous city in the state, with a census-estimated 2015 population of 209,175 within an area of 18.0 square miles the city is the third-largest in the Tampico metropolitan area. It is also an important center for oil refining.