State Route 121 (SR 121) is a 36-mile-long (58 km) state highway in southern Maine. It begins at an intersection with U.S. Route 302 (US 302) and SR 35 in Raymond and ends in Auburn. It is signed as a north-south highway, which accurately reflects its alignment from Raymond to Oxford, but from there it runs almost due east (and slightly south) to its terminus in Auburn.