Thorite, (Th,U)SiO4, is a rare nesosilicate of thorium that crystallizes in the tetragonal system and is isomorphous with zircon and hafnon.

Thorite was discovered in 1828 on the island of Løvøya, Norway, by the vicar and mineralogist, Hans Morten Thrane Esmark.

First specimens of Thorite were sent to his father, Jens Esmark, who was a professor of mineralogy and geology.

It is commonly associated with zircon, monazite, gadolinite, fergusonite, uraninite, yttrialite and pyrochlore.

With the destructive effects of radioactivity on the crystal lattice, hydrated specimens are often amorphous and optically isotropic.