The Maine River is a river located in the state of Maine, USA. It is composed of three main rivers: the Saco, Kennebec and Penobscot. The Saco River is a short river that flows through New Hampshire and Maine, and is approximately 84 miles long. The Kennebec River is a 170-mile-long river that runs through Maine and empties into the Atlantic Ocean. The Penobscot River is the longest river in Maine, stretching for over 200 miles and emptying into the Gulf of Maine. All three rivers are important sources of water for the state of Maine.