Yucatán, estado (state), southeastern Mexico. Occupying part of the northern Yucatán Peninsula, it is bounded to the north by the Gulf of Mexico, to the east and southeast by the state of Quintana Roo, and to the southwest and west by the state of Campeche. The state capital and chief commercial centre is Mérida.

The state’s relief includes coastal wetlands, semiarid hills and plains, and limestone lowlands dotted with cenotes (water-filled sinkholes). In pre-Hispanic times the peninsula was an Olmec and Maya cultural hearth, as evidenced by the monumental ruins of Chichén Itzá and Uxmal; each has been designated a UNESCO World Heritage site, in 1988 and 1996, respectively. Among the other numerous ruined cities are Chumul, Ek Balam, and Sayil. Strong resistance to the Spanish conquest lasted in the area from 1527 until the 1540s. Yucatán occupied the entire peninsula when it became a state in 1824, but following a series of insurrections, its territory was reduced with the loss of Campeche in 1857 (ratified in 1858) and Quintana Roo in 1902. Later boundary changes reduced the state to its present size.