Mill Bay is a census-designated place (CDP) in Kodiak Island Borough, Alaska, United States. It was first listed as a CDP prior to the 2020 census. As of the 2020 census, Mill Bay had a population of 4,216.
Mill Bay is located at the northeast tip of Kodiak Island, surrounding the small bay for which the community is named. It is bordered to the southwest by the city of Kodiak.
According to the United States Census Bureau, the Mill Bay CDP has a total area of , of which are land and , or 4.62%, are water.
As of the 2020 census, the population of the CDP is 4,216. It is the second most populated place in the borough.