Trexler Run is a tributary of Little Catawissa Creek in Columbia and Schuylkill counties in Pennsylvania, in the United States.

The stream is considered to be a High-Quality Coldwater Fishery and Class A Wild Trout Waters.

Trexler Run begins in a valley on Little Mountain in Roaring Creek Township, Columbia County.

It flows south-southeast for several tenths of a mile, exiting Roaring Creek Township and Columbia County.

It continues south-southeast, crossing State Route 4036, for a short distance before receiving an unnamed tributary and turning east in a valley.

After some distance, it crosses State Route 4036 again and continues east and slightly north.

[1] Trexler Run joins Little Catawissa Creek 4.24 miles (6.82 km) upstream of its mouth.

[3] At 1:10 P.M. on June 30, 1997, the air temperature in the vicinity of Trexler Run 0.80 miles (1.29 km) upstream of its mouth was 28 °C (82 °F).

[3] The discharge of Trexler Run near Ringtown has been measured by the United States Geological Survey several times.

The southern and central parts of the watershed, including most of the stream's length, are on Leck Kill soil.

[3] There is some land belonging to Nature Conservancy Priority Forest Hubs found in the northern part of the watershed.

[3] 50 percent of the length of Trexler Run is on private land that is open to fishing.

[3] Trexler Run has been surveyed by the Pennsylvania Fish and Boat Commission three times.

The first was performed by Shoemaker in 1932 and advised against stocking the stream on account of its small size.

[3][7] Additionally, it is considered by the Pennsylvania Fish and Boat Commission to be Class A Wild Trout Waters.

[3] The brook trout inhabiting Trexler Run range from 50 to 249 millimeters in length.

[3] Trexler Run is one of two streams in the watershed of Catawissa Creek with a significant population of brown trout.