State Route 154 (SR 154) (also known as the Chumash Highway or unofficially as San Marcos Pass Road after the signage) is a state highway in the U.S. state of California that runs from Los Olivos to Santa Barbara, crossing the San Marcos Pass in the Santa Ynez Mountains. Before U.S. Route 101 was built through the Gaviota Pass, SR 154 was the main throughway to Santa Barbara and the tri city area including use as a stagecoach route in early years. After being replaced by US 101 as the primary route between the Santa Ynez Valley and Santa Barbara, SR 154 now serves as a scenic bypass.