State Route 421 (SR 421) is a two-lane east-west state highway in the north-central portion of Ohio. Existing entirely within Medina County, State Route 421's endpoints are at opposite ends of the concurrency of U.S. Route 42 and U.S. Route 224, which together form the four-lane bypass of Lodi. State Route 421 serves both as a de facto business route for U.S. Route 42 and U.S. Route 224 for Lodi, as well as a connector between the two U.S.