Neuston is the collective term for the organisms that float on the top of water. Neustons are made up of some species of beetles, protozoans, bacteria and spiders.

By extension, the term may also refer to non-organismal floating aggregations (see, e.g., Great Pacific Garbage Patch).

Contrast the terms plankton (the organisms that float or drift within the water), nekton (the organisms that swim (powerfully) in the water), and benthos (the organisms on the bottom of a body of water).