Pacheco Pass, Mountain pass in California, United States.

Pacheco Pass is a mountain passage in the Diablo Range that connects the Santa Clara Valley with the Central Valley through State Route 152 at roughly 1,368 feet elevation. The pass cuts through wooded and open hillsides, with the four-lane highway climbing toward the summit to cross between the two valleys.

Gabriel Moraga, a Spanish army officer, first recorded the pass in 1805. In 1857 Andrew D. Firebaugh built a wagon road with a gentler grade across the steep east face, replacing a rough horse and mule trail. From 1858 to 1861 the Butterfield Overland Mail stagecoach route passed through Pacheco Pass Station. The pass is California Historical Landmark #829.

The name comes from Don Francisco Pérez Pacheco, owner of Rancho Ausaymas y San Felipe; in the 1850s travellers called it Robber's Pass after the hold-ups on the road. A Yokuts trail through what is now Pacheco State Park crossed the mountains for trade with coastal peoples, and in the 1820s and 1830s Native Americans came west over the pass to raid missions and ranchos for horses and cattle.

Pacheco Pass Road runs about 14 miles from Gilroy to the summit, two lanes to the SR 156 junction and four lanes over the pass; this stretch has a record of many accidents. Entrances to San Luis Reservoir and Pacheco State Park have no stop signs or traffic lights, so turning across two lanes of heavy traffic in each direction needs care. No major community lies between Gilroy and Los Banos except Santa Nella, at the SR 33 junction.

A 16 MW wind farm of 162 turbines stands at the top of the pass, visible from Dinosaur Point Road. It is being repowered to 147 MW, paired with a 50 MW / 200 MWh grid battery. The California High-Speed Rail is planned to run beneath the pass in the 13-mile Pacheco Pass Tunnels, expected to become North America's longest rail tunnels.