The river is formed at Johnsonburg in central Elk County by the confluence of its East and West Branches.
The East Branch, approximately 15 mi (24 km) long, rises in northeastern Elk County and flows southwest through East Branch Clarion River Lake to join the West Branch.
The river flows generally west-southwest across western Pennsylvania in a tight meandering course past Ridgway and Clarion.
It joins the Allegheny from the east in western Clarion County approximately 5 mi (8 km) south of Emlenton.

The Clarion is a designated part of the National Wild and Scenic River program.
The river is formed at Johnsonburg in central Elk County by the confluence of its East and West Branches. The East Branch, approximately 15 mi (24 km) long, rises in northeastern Elk County and flows southwest through East Branch Clarion River Lake to join the West Branch. The river flows generally west-southwest across western Pennsylvania in a tight meandering course past Ridgway and Clarion. It joins the Allegheny from the east in western Clarion County approximately 5 mi (8 km) south of Emlenton.
The Clarion is a designated part of the National Wild and Scenic River program.
Clarion River