Clarkeite is a uranium oxide mineral with the chemical formula(Na,Ca,Pb)2(UO2)2(O,OH)3 or (Na,Ca,Pb)(UO2)O(OH)·0-1H2O.

Its color varies from dark brown to reddish orange.

Clarkeite forms by oxidation and replacement of uraninite late during pegmatite crystallization.

Although uraninite-bearing granite pegmatites are common, clarkeite is rare and occurs intimately intergrown with other uranium minerals.

It was named for Frank Wigglesworth Clarke (1847–1931), American mineral chemist, and former chief chemist of the United States Geological Survey.