The term 'Indiana River' refers to four rivers in the state of Indiana: the Maumee, Wabash, Ohio, and Wabash. The Maumee is a tributary of Lake Erie that flows through northwestern Ohio and northeastern Indiana. The Wabash is the longest river in Indiana, flowing from the Ohio River in southwestern Indiana to the Illinois border. The Ohio is a major tributary of the Mississippi River that forms the border between Indiana and Ohio. Finally, the Wabash is a tributary of the Ohio River that flows through western Indiana. All four of these rivers are important sources of water for the state of Indiana.