Leechburg is a borough in southern Armstrong County in the U.S. state of Pennsylvania, 35 miles northeast of Pittsburgh.

     Leechburg was founded by David Leech, for whom it was later named. Located along the Kiskiminetas River in a deep bend of the river, Leechburg was a major port of the Pennsylvania Canal, built from 1826 to 1829.
     Early in the 20th century, it was the site of extensive steel sheet works, foundries, cement plants, and productive coal mines. Leechburg was the first place where natural gas was used for industrial purposes.
     David Leech came to this place in 1827, having the contract to build the Pennsylvania canal dam, in partnership with a man named Trux. Leech used the water from this dam to run his flouring and saw mills and a woolen factory from 1829 to 1832. These mills, after David Leech's death, came into the hands of his son, Addison, and after him were operated by R. D. Elwood & Bro. In addition to the above-mentioned enterprises the founder of Leechburg was, soon after he settled here, engaged in the mercantile lines of trade and together with his sons was afterward extensively engaged in the same business.

     The borough of Leechburg was incorporated by act of March 22, 1850.