Hydrogaster

{{Short description|Genus of plants}}

{{Automatic taxobox

|image = Hydrogaster_trinervis_Kuhlm._(16032953094).jpg

|image_caption =Hydrogaster trinervis Kuhlm

|taxon = Hydrogaster

|image_alt = Colour photograph of a green Hydrogaster trinervis Kuhlm leaf and twig with small white flowers and small white flower buds on the end. the leaf and twigs are being held between the fingers of a man

|authority = Kuhlm.

}}

Hydrogaster is a monotypic genus of flowering plants belonging to the family Malvaceae. It only contains one species, Hydrogaster trinervis Kuhlm. {{cite web |title=Hydrogaster Kuhlm. {{!}} Plants of the World Online {{!}} Kew Science |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:297405-2 |website=Plants of the World Online |access-date=16 May 2021 |language=en}}

Its native range is eastern Brazil.