State Route 123 (SR 123) is a state highway in the U.S. state of California in the San Francisco Bay Area. Named San Pablo Avenue for virtually its entire length, SR 123 is a major north–south state highway along the flats of the urban East Bay. Route 123 runs about 7.39 miles (11.9 km) between Interstate 580 in Oakland in the south and Interstate 80 in Richmond in the north. San Pablo Avenue itself, a portion of Historic US 40, continues well past these termini, south to Downtown Oakland and north to Crockett, but without the Route 123 designation.