San Marcos Pass is a mountain pass in the Santa Ynez Mountains in southern California. It is traversed by State Route 154. The pass crosses the Santa Ynez through a southwestern portion of Los Padres National Forest, and connects Los Olivos with Santa Barbara, California along the Pacific coast. The road has been designated as a daylight-headlight highway by the California Highway Patrol and Caltrans because of frequent accidents, particularly around the exit for Lake Cachuma.