The Breen Ambassador to the United Federation of Planets is the individual in the government of the Breen Confederacy responsible for representing his or her state to the United Federation of Planets.
In 2375, the Breen Ambassador to the Federation was withdrawn upon the Breen Confederacy's alliance with the Dominion and attack on Earth. (TNG short story: "Eleven Hours Out")
By 2381, the Federation and Breen were exchanging ambassadors again. That year, the Breen Ambassador was Gren. (ST - Destiny novel: Mere Mortals)