The ionization of fluorine with a field ion source is demonstrated. A fluorine(10%)–helium(90%) gas mixture and a (110) oriented tungsten emitter are used. The ion source is operated at a pressure of 1.5×10−5Torr and at temperatures between 7 and 80 K using a (110) plane of the emitter. Two current peaks in theI–Vcharacteristics are observed at temperatures over 46 K and one of them is confirmed to correspond to fluorine ion emission, which shows a maximum at 52 K and has an angular current density of 1.5×10−6A/sr and a brightness of 6×108A/cm2 sr. TheI–Vcharacteristics’ dependency on the crystal planes of the emitter tip such as (111) and (121) are also presented.