Etna is a borough in Allegheny County, Pennsylvania, United States, located across the Allegheny River from Pittsburgh. The population was 3,437 at the 2020 census. It is a suburb of the Pittsburgh metropolitan area.

The Allegheny River is a 325-mile-long (523 km) headwater stream of the Ohio River that is located in western Pennsylvania and New York in the United States. It runs from its headwaters just below the middle of Pennsylvania's northern border, northwesterly into New York, then in a zigzag southwesterly across the border and through Western Pennsylvania to join the Monongahela River at the Forks of the Ohio at Point State Park in Downtown Pittsburgh, Pennsylvania.