Tonina fluviatilis is a plant species in the Eriocaulaceae.

It is the sole species in the monotypic genus Tonina, native to southern Mexico, Central America, northern South America (Colombia, Venezuela, Ecuador, Peru, northern Brazil, and the Guianas), Cuba and Trinidad.

The plant is ground up and mixed with a bark to make a liquid in which to bathe nursing infants.

[7] The shape of its leaf is pleasing and its color makes a good contrast with other plants when it is planted in small groups.

However, it is difficult to grow as an aquarium plant.