The Cialitos River () is a tributary of the ManatÃÂ River (RÃÂo Grande de ManatÃÂ) that flows through the municipality of Ciales, Puerto Rico. Its headwaters are located in the northward slopes of Los Tres Picachos massif of the Cordillera Central, from where it flows towards the Northern Karst belt of Puerto Rico, where it meets the ManatÃÂ River by Ciales Pueblo.
The Cialitos River Nature Reserve (Reserva Natural RÃÂo Cialitos) was established in 1999 to protect the forested tracts along the stretch of the river that represents an ecological corridor between the Cordillera Central and the Northern Karst of Puerto Rico. In addition to its ecological value, this area also represents a geological transition stage between the volcanogenic Cordillera Central and the karst zone. The heterogeneous nature of the area is reflected in its high biodiversity, with endemic species such as the Puerto Rican sharp-shinned hawk. The headwaters of the Cialitos River are also protected as part of the Los Tres Picachos State Forest.