Tlalnepantla de Baz (tlälnāpänˈtlä ħā bäs) [key], city (1990 pop. 702,270), Mexico state, S central Mexico, on the Tlalnepantla River. It is a communications and industrial center that owes its importance largely to its proximity to Mexico City. Smelting, metalworking, machine-building, and chemical manufacturing are among the chief industries. There are important archaeological ruins nearby.