Mad River (California)

The Mad River is a river in upper Northern California. It flows for in a roughly northwest direction through Trinity County and then Humboldt County, draining a watershed into the Pacific Ocean north of the college town of Arcata near Arcata-Eureka Airport in McKinleyville. The river's headwaters are in the Coast Range near South Kelsey Ridge.

Mad River (formerly, Kuntz) is a census-designated place (CDP) in Trinity County, California. Mad River is located in the in southern part of the county. Mad River sits at an elevation of . The ZIP Code is 95552 and Mad River is the furthest east town in area code 707. The 2010 United States census reported Mad River's population was 420.