Alpharetta is a city in northern Fulton County, Georgia, United States, and part of the Atlanta metropolitan area. As of the 2020 U.S. census, Alp…Alpharetta is a city in northern Fulton County, Georgia, United States, and part of the Atlanta metropolitan area. As of the 2020 U.S. census, Alpharetta's population was 65,818; in 2010, the population had been 57,551.