The Gaviota Tunnel (officially known as the Gaviota Gorge Tunnel) is a tunnel on U.S. Route 101 completed in 1953 in the center of Gaviota State Park, 33 miles (53 km) northwest of Santa Barbara, California. It is 420 feet (130 m) long and 17.5 feet (5.3 m) tall. Only the northbound lanes of U.S. Route 101 (El Camino Real) pass through it, as the southbound lanes descend from Gaviota Pass through a narrow canyon to the west of the tunnel. Because it is the only major route between the Santa Barbara County South Coast and the Santa Ynez Valley, bicycles are allowed through it. There is a rest area on the southern end of the tunnel, the southernmost one along U.S. Route 101.
There are frequent rockslides in the area, especially during and following rain. Some of the hillsides and road cuts are covered in netting to prevent erosion. There are also fences made of netting along the roadway to stop rocks that do fall.
An alternate bypass to this section of U.S. Route 101 between Santa Barbara and Los Olivos is provided by State Route 154 capped by the Cold Spring Canyon Arch Bridge near the summit of San Marcos Pass. Highway 154 cuts directly between Santa Barbara and Los Olivos in a northwestern direction, whereas highway 101 runs along the coast of the Pacific Ocean about 25 miles (40 km) west before turning north passing through Buellton to meet up with highway 154 near Los Olivos.