Petersburg
- Country: United States
- State: Alaska
- Population: 2,948 (2010)
- Latitude: 56° 48.7' N (56.81127°)
- Longitude: 132° 57.1' W (-132.95124°)
- Elevation: 19 m/63 ft. above sea level
- Time zone: America/Sitka (UTC -09:00); DST observed (UTC -08:00)
- Alternate names: Petersburg CDP, Seet Ka