Blawnox is a borough in Allegheny County, Pennsylvania, United States.

The name, Blawnox, is derived from the Blaw-Knox Company, which had a manufacturing plant there providing much of the town's employment.

[6] Blawnox is entirely surrounded by land to the north, northeast and west by the westernmost section of O'Hara Township.

Across the Allegheny River, Blawnox runs adjacent with Penn Hills.

There were 931 housing units at an average density of 2,866.0 per square mile (1,106.6/km2).

51.3% of all households were made up of individuals, and 19.1% had someone living alone who was 65 years of age or older.