Fairmont Butte, Volcanic butte in Antelope Valley, Los Angeles County, US

Fairmont Butte is a volcanic butte in the Antelope Valley west of Lancaster, Los Angeles County, California. Its summit reaches 3,130 feet above sea level, about 114 metres above the surrounding terrain, and parts of it lie within the Antelope Valley California Poppy Reserve. The rock is volcanic tuff, the material quarried for cement during construction of the Los Angeles Aqueduct.

Los Angeles City administration opened a quarry at the site in the early 1900s to mine volcanic tuff for cement production. This industrial use shaped the landscape for decades before the area eventually became protected as a nature reserve.

Only parts of Fairmont Butte lie inside the Antelope Valley California Poppy Reserve, so the butte is not wholly within the protected land. The butte's name comes from the nearby community of Fairmont, and the tuff quarried at its base went into the Los Angeles Aqueduct's Mojave conduit.

Only parts of Fairmont Butte lie inside the Antelope Valley California Poppy Reserve, so check the reserve boundary before walking; the summit reaches 3,130 feet above sea level. The butte rises about 114 metres above the surrounding plain and is roughly 2 km wide at its base. The terrain around it is mostly flat desert, with the higher Burnt Peak about 17 km to the east.

The tuff mined here was ground and blended with Portland cement at a plant built at the butte's base, and the resulting mix went into the Mojave conduit of the Los Angeles Aqueduct. Los Angeles opened the quarry because the stone closely matched German Trass and Italian Pozzolana.