Tybee Island is a city and a barrier island in Chatham County, Georgia, 18 miles east of Savannah. The name is used for both the city and the is…Tybee Island is a city and a barrier island in Chatham County, Georgia, 18 miles east of Savannah. The name is used for both the city and the island, but geographically the two are not identical: only part of the island's territory lies within the city, while the rest is unincorporated.