Hexafluorotitanic acid (systematically named oxonium hexafluoridotitanate(2-)) is an inorganic compound with the chemical formula (H<sub>3</sub>O)(H<sub>5</sub>O<sub>2</sub>)[TiF<sub>6</sub>]. According to X-ray crystallography, the salt consists of [TiF<sub>6</sub>]<sup>2-</sup> octahedral and two kinds of oxonium cations, (H<sub>3</sub>O)<sup>+</sup> and (H<sub>5</sub>O<sub>2</sub>)<sup>+</sup>.
As with most oxonium salts, it is only stable in acidic solution. Under basic conditions, closely related salts hydrolyse to a hydrated titanium dioxide:
A related salt is the anhydrous fluoronium hexafluoridotitanate(2-) or (H<sub>2</sub>F)<sub>2</sub>[TiF<sub>6</sub>].