State Route 203 (SR 203) is a state highway in the U.S. state of Washington that traverses part of King and Snohomish counties. It runs north–south through the Snoqualmie Valley, connecting Fall City, Carnation, Duvall, and Monroe. The highway terminates to the south at a roundabout with SR 202 near Fall City and to the north at a junction with U.S. Route 2 (US 2) in Monroe.