North Branch Calvin Run is a long first-order tributary to Calvin Run in Greene County. This is the only stream of this name in the United States.
North Branch Calvin Run rises about 2 miles southeast of Kirby, Pennsylvania and then flows southerly to join Calvin Run about 2 miles northwest of Mount Morris, Pennsylvania.
North Branch Calvin Run drains of area, receives about 43.1 in/year of precipitation, and is about 78.8% forested.