Río Parismina, River system in Limón Province, Costa Rica.

The Río Parismina rises on the Turrialba volcano and joins the Reventazón at the start of its 21 km navigable stretch to the Boca del Parismina on the Caribbean. Its basin, 2,950 km², is Costa Rica's third largest. The land around the mouth is almost flat, six metres above sea level, with the sea close to the northeast.

The Parismina rises on the Turrialba volcano and joins the Reventazón, whose combined basin covers 2,950 km², the third largest in Costa Rica. Its soils change downstream: ultisol in the upper and middle course, inceptisol in most of the lower course, and entisol near the Caribbean mouth. The river is navigable for 21 km from the Reventazón confluence to the Boca del Parismina.

The name Parismina comes from the river that marks the third-largest basin in Costa Rica, the Reventazón-Parismina, covering 2,950 km². At the Boca del Parismina, on the Caribbean mouth, residents and guides accompany nighttime turtle nesting, when green, leatherback and hawksbill turtles come ashore to lay eggs on the beach.

The river is navigable for 21 km from its confluence with the Reventazón to the Boca del Parismina. The mouth lies in Siquirres canton, Limón province, 90 km east of San José and 6 m above sea level; the surrounding terrain is very flat and the sea is close to the northeast. Boat access is by water from the Reventazón.

Seven Atlantic sea turtle species nest at the mouth of the Parismina, among them the green turtle (Chelonia mydas), the leatherback (Dermochelys coriacea) and the hawksbill (Eretmochelys imbricata). The beach at the Boca del Parismina is where the spawning is most concentrated, which is why the site is watched for its ecological value.