Geddes Run is a tributary of the Tohickon Creek contained wholly within Plumstead Township, Bucks County, Pennsylvania, in the United States.
The first inhabitants of the area of Geddes Run were the Lenape people. Many artifacts have been found, including 'turtlebacks' fashioned by the Lenape people from a quarry in the area of Geddes Run. The region became part of the Walking Purchase of the family of William Penn in 1737.
The nearby 'bluestone' quarry was operated for many years by Nicholas L. Heaney, which supplied thousands of feet of flagstone and curbstone for Doylestown's streets until replaced by concrete.
On 24 August 1891, a storm occurred, which was officially measured in Doylestown at in 24 hours, causing Geddes Run to flood, resulting in severe damage in Point Pleasant, including the destruction of the Solomon Fulmer store and severe damage to the covered bridge over the Tohickon Creek.
Geddes Run is long, and a watershed of , part of the Delaware River watershed. It rises at an elevation of and its mouth elevation is , resulting in an average slope of . The GNIS I.D. number is 1175497, the U.S. Department of the Interior Geological Survey code number is 03111. Geddes Run meets its confluence at the Tohickon Creek's 0.30 river mile.
Geddes Run is northeast oriented for about half its length, then it turns to the southeast for a short distance then, as it turns back northeast, it picks up an unnamed tributary. It reaches the Tohickon Creek in Pleasant Valley about before the Tohickon flows into the Delaware River.
Geddes Run lies on the Lockatong Formation of rock formed during the Triassic, which consists of argillite, shale, and some impure limestone and calcareous shale.