Nymphaea pedersenii is a species of waterlily native to Argentina, Bolivia, Brazil, and Uruguay.

[3] The coriaceous blade of the floating leaves is connected to non-brittle, brownish, glabrescent, 7.1−10 mm wide petioles with a ring of trichomes at the apex.

[4] The syncarpous gynoecium consists of approximately 39 carpels with clavate, cream-coloured, curved, 1.2−1.8 cm long and 2−4 mm wide appendages.

[1] The type specimen was collected by Wiersema, Vanni and Schinini in a lagoon in Itatí, Corrientes, Argentina on the 15th of April 1982.

[3] In Brazil, it was observed in a stream with up to 3 m depth in the state Pará and in permanent or temporary lagoons in the Pantanal.