Thermonectus

{{Short description|Genus of beetles}}

{{Automatic taxobox

| image = Sunburst Diving Beetle (Thermonectus marmoratus) with air bubble - San Diego Natural History Museum.jpg

| image_caption = Thermonectus marmoratus

| display_parents = 2

| taxon = Thermonectus

| authority = Dejean, 1833

}}

Thermonectus is a genus of beetles in the family Dytiscidae. This genus is native to the New World, and mainly from warm temperate to tropical in distribution, but one species, T. basillaris occurs as far north as southern Ontario, Canada.{{cite book |first1=D. J. |last1=Larson |first2=Y. |last2=Alarie |first3=R. E. |last3=Roughley |title=Predaceous diving beetles (Coleoptera: Dytiscidae) of the Nearctic Region, with emphasis on the fauna of Canada and Alaska |publisher=Natural Research Council of Canada |year=2000 |isbn=0-660-17967-9}} They inhabit a wide range of freshwater habitats with static water and are often common.{{cite book| author1=Miller, K.B. |author2=J. Bergsten | title=Diving Beetles of the World: Systematics and Biology of the Dytiscidae | year=2016 | pages=131–132 |publisher=JHU Press | isbn=978-1-4214-2054-7 }} They are generally about {{convert|0.8-1.5|cm|in|abbr=on|1}} long and a few species from desert pools in North America have a distinct yellow-spotted pattern on a black background.