Chemical reaction of F atoms with O-3 molecules in a solid argon matrix was studied with FTIR spectroscopy. Fluorine atoms were generated by UV photolysis of F-2 molecules in dilute solutions of F-2 and O-3 in solid argon. The FO-O-2 complex is observed for the first time as an intermediate product by reaction of mobile F atoms with isolated ozone molecules. The observed complex is characterized by two intense absorption bands at 1522 and 968 cm(-1). Use of isotopic mixtures O-16/O-18 provides strong evidence for assignment of these bands to the O-O stretch and F-O stretch fundamentals of the complex, which are red-shifted by 34 and 61 cm(-1), respectively, from the corresponding values for O-2 and FO. Photolysis at 532 nm leads to decay of the FO-O-2 complexes and to the appearance of isolated free FO radicals.