Notodiaptomus is a genus of copepods in the family Diaptomidae. It is the most widely distributed, most abundant and most species-rich genus of freshwater calanoid copepods in the Neotropics. The genus was erected in 1936 by Friedrich Kiefer for eleven species formerly placed in a wider Diaptomus. Notodiaptomus deitersi was chosen to be the type species by Raúl Adolfo Ringuelet in 1958.

The genus Notodiaptomus includes 34 valid species, and two species inquirenda. Its members include the Venezuelan endemic Notodiaptomus maracaibensis and the Brazilian endemic Notodiaptomus dubius, both of which are listed as vulnerable species on the IUCN Red List.

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