Kupreanof is a city on the eastern shore of Kupreanof Island in the Petersburg Borough, in the U.S. state of Alaska. The population was 21 as of the 2020 census, down from 27 in 2010. It is the smallest incorporated city in the state as of 2020.

Petersburg Borough is a borough in the U.S. state of Alaska. According to the 2020 census, the population was 3,398. The borough seat is Petersburg.