Port Alsworth is a census-designated place (CDP) in Lake and Peninsula Borough, Alaska, United States. It is 165 miles (266 km) by air southwest of Anchorage. The population was 186 at the 2020 census, up from 159 in 2010. It is the most populated community in the borough.

Lake and Peninsula Borough is a borough in the state of Alaska. As of the 2020 census, the population was 1,476, down from 1,631 in 2010. The borough seat of King Salmon is located in neighboring Bristol Bay Borough, although is not the seat of that borough. The most populous community in the borough is the census-designated place of Port Alsworth. With an average of 0.017 inhabitants per square kilometre, the Lake and Peninsula Borough is the second least densely populated organized county-equivalent in the United States; only the unorganized Yukon-Koyukuk Census Area has a lower density.