Iodine monofluoride is an interhalogen compound of iodine and fluorine with formula IF.

It is a chocolate-brown solid that decomposes at 0 °C,[1] disproportionating to elemental iodine and iodine pentafluoride: However, its molecular properties can still be precisely determined by spectroscopy: the iodine-fluorine distance is 190.9 pm and the I−F bond dissociation energy is around 277 kJ mol−1.

At 298 K, its standard enthalpy change of formation is ΔfH° = −95.4 kJ mol−1, and its Gibbs free energy is ΔfG° = −117.6 kJ mol−1.

It can be generated, albeit only fleetingly, by the reaction of the elements at −45 °C in CCl3F: It can also be generated by the reaction of iodine with iodine trifluoride at −78 °C in CCl3F: The reaction of iodine with silver(I) fluoride at 0 °C also yields iodine monofluoride: Iodine monofluoride is used to produce pure nitrogen triiodide:[2]