The Sierra de Luquillo (English: "Luquillo Mountains") is a steep-sided, high-precipitation, and deeply-forested subrange of the Cordillera Central mountain range in the main island of Puerto Rico. Separated from the southeastern Sierra de Cayey subrange by the Caguas Valley, it is concentrated from west to east in the municipalities of Rio Grande, Luquillo, and Naguabo in the northeastern region of the island. The summit of the mountain range is El Toro at 3,526 ft. (1,075 m), and its most recognizable peak is El Yunque at 3,461 ft. (1,054 m). As the location of El Yunque National Forest, the Sierra de Luquillo is a popular destination among domestic and foreign tourists.
Along with the eponymous main subrange of Cordillera Central and the Sierra de Cayey, the Luquillo mountain range is one of three subranges of the Cordillera Central. However, although a subrange of the Cordillera Central, the Sierra de Luquillo is occasionally considered to be different from the rest of the central mountain range, as it is separated from it by the Caguas Valley and the Rio Grande de LoÃza basin.