The Monterey County Rail Extension is a planned commuter rail extension that would bring Caltrain passenger service south of its existing Gilroy, California terminus to Salinas in Monterey County, using the existing Coast Line owned by Union Pacific (UPRR). Implementation of the rail extension will occur over three phases, starting from Salinas and moving north. When construction is complete, there will be four trains operated over the extended line per weekday: two northbound trains that depart from Salinas and travel to San Francisco in the morning, and two southbound trains that return to Salinas in the afternoon.

Gilroy is a city in Northern California's Santa Clara County, south of Morgan Hill and north of San Benito County. Gilroy is the southernmost city in the San Francisco Bay Area, with a population of 59,520 as of the 2020 Census.