The Prieto River is a river in Lares, Puerto Rico.

During the Spanish-American War (1898), a number of Spanish soldiers drowned in this river:^[2]

I overtook him Saturday morning about three and one-half miles north of Las Marias. His infantry had pulled his guns over roads that were almost perpendicular. His troops were exchanging shots at long range across a deep valley with the retreating Spaniards, most of whom had forded (losing a lot of men, who were drowned) a deep and rapid river known in that country as the Rio Prieto. Our fire had already demoralized the thoroughly disheartened and half-famished Spanish soldiers; and their rear-guard, at least, was also disorganized and hiding in the hills.

• List of rivers of Puerto Rico

• USGS Hydrologic Unit Map – Caribbean Region (1974)
• Ríos de Puerto Rico (in Spanish)