The West Branch Penobscot River is a  tributary of Maine's Penobscot River. The river flows from Seboomook Lake in Seboomook, Somerset County; the lake's principal inflows are the North Branch and South Branch Penobscot River. From Seboomook Dam the river runs about east and northeast to Chesuncook Lake, thence (after flowing through Chesuncook) about southeast through the southwest corner of Baxter State Park to the Pemadumcook Chain of Lakes, thence generally east to its confluence with the Penobscot's East Branch in Medway, Penobscot County.