Quintana Roo state, southeastern Mexico, on the eastern side of the Yucatán Peninsula. Its northern shore is on the Yucatán Channel, a passage between the Gulf of Mexico and the Caribbean Sea; it is also bounded by the Caribbean to the east, by Belize and Guatemala to the south, by the state of Campeche to the west, and by the state of Yucatán to the northwest. The state capital, Chetumal, is located on a sheltered bay at the mouth of the Hondo River, on the frontier with Belize.

Quintana Roo occupies a hot, humid, and heavily forested lowland dotted with cenotes (water-filled sinkholes) and limestone caves. The state administers the coastal islands of Contoy, Mujeres, and Cozumel, among others, as well as cays and reefs off the Caribbean