The fluoronium ion is an inorganic cation with the chemical formula H2F+.

The term can also refer to organyl substituted species of type H–+F–R, R–+F–R, or R2C=F+.

[5] Recent solvolysis experiments and NMR spectroscopic studies on a metastable [C–F–C]+ fluoronium ion strongly support the dicoordinated fluoronium structure over the alternative rapidly equilibrating classical carbocation.

Definitive structural proof of the symmetrical [C–F–C]+ was reported by Riedel, Lectka, and coworkers by single crystal X-ray diffraction analysis.

Besides its synthesis and crystallographic characterization as the [Sb2F11]− salt, vibrational spectra could be recorded and a detailed analysis concerning the nature of the bonding situation in this fluoronium ion and its heavier halonium homologues was reported.