Valley Link is a proposed 26-mile-long (42 km) commuter rail service in Northern California, which seeks to connect the rapid transit Bay Area Rapid Transit (BART) system in the San Francisco Bay Area with the northern San Joaquin Valley via the Tri-Valley region. Since 1997, BART's Blue Line's eastern terminus is at Dublin/Pleasanton station on the border of Dublin and Pleasanton. Valley Link seeks to extend rail service east from here into the northern San Joaquin Valley over Altamont Pass and to help alleviate traffic congestion and reducing greenhouse gas emissions on Interstate 580 (I-580). The project resulted from various failed proposals to extend the Blue Line east to Livermore.

The Tri-Valley area is grouping of three valleys in the East Bay region of California's Bay Area. The three valleys are Amador Valley, San Ramon Valley, and Livermore Valley. The Tri-Valley encompasses the cities of Dublin, Livermore, Pleasanton and San Ramon, the town of Danville and the CDPs of Alamo, Blackhawk and Diablo. The area is known for its Mediterranean climate, wineries, and nature. It is primarily suburban in character. The United States Census Bureau defines an urban area centered in the cities of Livermore, Pleasanton, and Dublin with a 2020 population of 240,381, ranked 167th in the United States in terms of population. The total population of the area is estimated to be 361,000. It offers more affordable living accommodations than the cities of San Francisco and San Jose.