The Commonwealth of Puerto Rico (Spanish: Estado Libre Asociado de Puerto Rico) is a self-governing unincorporated organized territory of the United States located east of the Dominican Republic in the northeastern Caribbean. Puerto Rico, the smallest of the Greater Antilles, includes the main island of Puerto Rico and a number of smaller islands and keys, including Mona, Vieques, and Culebra.

The archipelago of Puerto Rico consists of the main island of Puerto Rico and various smaller islands, including Vieques, Culebra, Mona, Desecheo and Caja de Muertos. Of the latter five, only Culebra and Vieques are inhabited year-round. Mona is uninhabitated through large parts of the year except for employees of the Puerto Rico Department of Natural Resources. People can visit the island for hiking and camping by getting the required permits.

The mainland measures some 170 km by 60 km (105 miles by 35 miles). It has a population of approximately 4 million. The capital city, San Juan, is located on the main island's north coast and has a population of approximately 430,000.

The mainland is mostly mountainous with coastal areas in the north and south regions of the island. The main mountainous range is called "La Cordillera Central" (The Central Range). The highest elevation point of Puerto Rico, Cerro de Punta (1338 meters), is located in this range. Another important mountain range is the El Yunque National Forest with a maximum elevation of 1,065m.

Puerto Rico has nine lakes and more than 50 rivers. Most of these rivers are born in the "Cordillera Central." The rivers in the northern region of the island are bigger and with higher flow capacity than those of the south region.