State Route 121 (SR 121) is a California state highway in the Wine Country that runs northerly from its junction with State Route 37 at Sears Point, past the Tolay Lake basin and across Tolay Creek near Infineon Raceway, veers east at a junction with State Route 116 and Bonneau Road at Schellville, runs eastward through the Carneros region of the southern Sonoma Valley and Napa Valley (concurrent first with State Route 12, then with State Route 29), then northeastward to end near Lake Berryessa in Napa County.