Petersburg Census Area was a census area located in the U.S. state of Alaska. It was part of the unorganized borough and therefore had no borough seat, although its largest community was Petersburg. The population was 3,815 at the 2010 census. It was previously known as the Wrangell-Petersburg Census Area until June 1, 2008, when Wrangell, formerly a part of the census area, was incorporated as a city-and-borough. The Petersburg Census Area ceased to exist in 2013 when Petersburg incorporated as a borough, although Kake and several other parts of the former census area, including Tracy Arm, remain unorganized. A map of the old Petersburg Census Area boundaries can be seen here:

The census area had a total area of , of which of it was land and of it (42.3%) was water.