Ojo de Agua is the largest town in the municipality of Tecámac in Mexico State, Mexico. It is located in the northeastern part of the state, northeast of the Federal District (Distrito Federal) and within the Greater Mexico City urban area. It had a 2010 census population of 242,272 inhabitants, or 66.45 percent of its municipality's total of 364,579. Ojo de Agua is the largest locality in Mexico that is not a municipal seat.