Hydatellales is a botanical name for an order of flowering plants. In the Cronquist system, 1981, the name was used for an order placed in the subclass Commelinidae in class Liliopsida [=monocotyledons]. The order consisted of one family only:
- order Hydatellales
- family Hydatellaceae
The APG II system assigns these plants to the order Poales, close to the grasses and sedges. Recent study by Saarela et al., however, suggests a position out of the Poales; here, the Hydatellaceae link with the waterlilies, the first time a plant has been ejected from the monocots. The Angiosperm Phylogeny Website  had since updated the Nymphaeales page to include the family.
- Saarela, Jeffery M., Hardeep S. Rai, James A. Doyle, Peter K. Endress, Sarah Mathews, Adam D. Marchant, Barbara G. Briggs & Sean W. Graham. 2007. Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree. Nature 446:312-315.
- Stevens, P. F. (2001 onwards). Nymphaeales. Angiosperm Phylogeny Website. Version 7, May 2006. Accessed 21 March 2007.