Ohio State Route 190 is a short north-south route in Putnam County, and in the northwestern corner of Allen County. It connects Delphos and Fort Jennings, two towns northwest of Lima. The southern end is at Ohio Route 66 in Delphos, at an intersection with Lincoln Highway, or the former alignment of US Route 30. Ohio Route 66 comes from the south to turn west along Lincoln Highway for a short while, and at this point, Ohio Route 190 begins heading in the opposite direction along Lincoln Highway. It uses Lincoln Highway to get to a northerly road out of Delphos. That road winds northerly and northwesterly through Fort Jennings, where it meets Ohio Route 189 and Ohio Route 634. The final stretch takes Ohio Route 190 north-northeasterly to US Route 224, which continues to Kalida.