Sunol (Spanish: Suñol) is an unincorporated census-designated place (CDP) in Alameda County, California, United States. The population was 913 at the 2010 census.
The small, rural town of Sunol located along Niles Canyon is well known for its historic railroad system, on which the tourist railroad Niles Canyon Railway makes an in-town stop and the Altamont Corridor Express passes en route to San Jose and the Central Valley.
Sunol, formerly Sunolglen, is named for Antonio Suñol. His adobe ranch house from the 1840s was located where the San Francisco water system's works now is located.
The first Sunol post office opened in 1871 and the name was changed to Sunolglen the same year. The name reverted to Sunol in 1920. The town's name is in honor of Antonio Suñol, first postmaster in nearby San Jose and part owner of the historical Rancho Valle de San Jose land grant that once contained the site of the town.
Sunol is located adjacent to two railroads and lies near the crossroads of Interstate 680 and State Route 84. These connect Sunol with Fremont to the south and west, Pleasanton to the north, and Livermore to the northeast. Sunol sits 17 miles (27 km) north of the center of San Jose and 32 miles (51 km) southeast of San Francisco.
The town lies near Alameda Creek at the northwest edge of the Sunol Valley.