Adelaida (pronounced as, and in the 19th century commonly spelled as Adelaide)[2] is an unincorporated community in San Luis Obispo County, California, United States.

[3] In the 1880s, the population of Adelaida was approximately 500, supported by the prospering Klau and Buena Vista mercury mines.

The town boasted a community center, saloon, dance hall, general store, and four schools.

The Adelaida School, located near the entrance to the Osgood Ranch on Chimney Rock Road, was built in 1917.

Although the quicksilver mines were in operation into the 1970s, most of the local businesses had long since relocated to Paso Robles.