The Mahoning Valley is a geographic valley encompassing the area of northeast Ohio and northwest Pennsylvania that drains into the Mahoning River. The Mahoning River empties into the Beaver River, which empties into the Ohio River. The Mahoning River flows through Lawrence and Mercer counties in Pennsylvania, and Columbiana, Mahoning, Trumbull, and Portage counties in Ohio. The three main tributaries of the Mahoning River are Mosquito Creek, West Branch, and Eagle Creek, all in Ohio.
The area around Youngstown, Ohio, is often called the Mahoning Valley or the Steel Valley.