Nenadkevichite is a rare silicate mineral containing niobium with the chemical formula (Na,Ca)(Nb,Ti)Si2O7·2H2O.

It forms brown to yellow to rose colored orthorhombic dipyramidal crystals with a dull to earthy luster.

It was first reported in 1955 from a nepheline syenite pegmatite in the Kola Peninsula.

In addition it has been reported from Mont Saint-Hilaire, Canada; the Ilimaussaq complex, Greenland; Windhoek District, Namibia; and Zheltye Vody, Ukraine.

It was named after Konstantin Avtonomovich Nenadkevich (1880–1963), Russian mineralogist and geochemist.