Stefani will join the Reckitt Benckiser brand's stable of celebrities with their own lines, including David and Victoria Beckham.
In July, Coty announced that it had signed a fragrance licensing deal with Kylie Minogue. Her first scent is expected to launch by the end of the year.
Stefani was on a list of celebrities found to be appealing to consumers in a recent survey carried out by The Proficiency Group.
Coty refused to confirm the deal with Stefani. It is not known when the fragrance will debut in the UK.