Thorium trifluoride is a binary inorganic compound of thorium metal and fluorine with the chemical formula .
Thorium trifluoride is not formed in a reaction of thorium metal with thorium tetrafluoride: Molecules of ThF<sub>3</sub> have been prepared by reacting atomic thorium with fluorine gas, and condensation onto a solid inert gas matrix. A solid phase is not known.