St. Clair is an unincorporated community and census-designated place (CDP) in Blair County, Pennsylvania, United States.

[2] The CDP is in eastern Blair County, in the southern part of Catharine Township.

Pennsylvania Route 866 passes through St. Clair, leading southeast 2 miles (3 km) to Williamsburg and northwest 1.5 miles (2.4 km) to U.S. Route 22 near Point View.

St. Clair sits at the southern base of Short Mountain, which rises 900 feet (270 m) above the community to an elevation of 1,790 feet (550 m).

This Blair County, Pennsylvania state location article is a stub.