Thoms Run is a long 2nd order tributary to Chartiers Creek in Allegheny County, Pennsylvania.
Thoms Run rises about 0.25 miles north of Beechmont, Pennsylvania and then flows southeasterly to join Chartiers Creek at Presto.
Thoms Run drains of area, receives about 38.4 in/year of precipitation, has a wetness index of 308.49, and is about 43% forested.