[3] The genus name honours Heinrich Bernhard Rupp, a German botanist (1688–1719).

They can be annual (commonly) or perennial (rarely); stem growth is conspicuously sympodial, but sometimes is not.

The minor leaf veins do not present phloem transfer cells and leaks vessels.

The scapiflorous inflorescences are terminal, in short spikes, or subumbelliform racemes, sometimes one- or few-flowered.

The androecium just presents two fertile stamens with sessile anthers dehiscing by longitudinal slits.

The fruiting carpel is indehiscent, commonly on a long, spirally twisted peduncle, with each drupelet becoming very long-stalked.

The Cronquist system of 1981 placed the family in order Najadales of subclass Alismatidae in class Liliopsida [=monocotyledons] in division Magnoliophyta [=angiosperms].

A genus-level taxonomy was briefly revised by Zhao and Wu,[7] including the following species in the world: Marine grasses families: Zosteraceae, Cymodoceaceae, Ruppiaceae and Posidoniaceae.

[19] These studies revealed that multiple hybridization and polyploidy events as well as chloroplast capture have occurred in the evolution of the genus.