State Route 111 (SR 111) is a 31.49-mile (50.68 km) state route that runs between the Indiana state line and Defiance in the US state of Ohio. Most of the route is a rural two-lane highway and passes through both farmland and residential properties. For some of its path, SR 111 runs generally parallel to the north of the Auglaize River. The highway was first signed in 1923 on much the same alignment as today.