Hydatellaceae are a family of small, aquatic flowering plants. The family consists of tiny, relatively simple, plants occurring in Australasia and India. It was formerly considered to be related to the grasses and sedges (order Poales), but has been reassigned to the order Nymphaeales as a result of DNA and morphological analyses showing its closer affinity to basal angiosperms than to the order Poales, to which it bears a superficial resemblance. The family includes only the genus Trithuria with 12 species (Christenhusz & Byng 2016 ). .