Thallium(I) fluoride is the inorganic compound with the formula TlF. It is a white solid, forming orthorhombic crystals. The solid is slightly deliquescent. It has a distorted sodium chloride (rock salt) crystal structure, due to the 6s<sup>2</sup> inert pair on Tl<sup>+</sup>.
This salt is unusual among the thallium(I) halides in that it is very soluble in water.
Thallium(I) fluoride can be prepared by the reaction of thallium(I) carbonate with hydrofluoric acid.