Mojave and Colorado Deserts Biosphere Reserve, Desert biosphere reserve in California, United States.

The Mojave and Colorado Deserts Biosphere Reserve is a UNESCO biosphere reserve designated in 1984, grouping four management units across the Mojave and Colorado deserts of California: Death Valley National Park, Joshua Tree National Park, Santa Rosa Mountains Wildlife Management Area and Anza-Borrego Desert State Park. Its boundaries are now unclear because Death Valley National Monument was expanded and reorganized into a national park, and the Santa Rosa Mountains unit became part of the Santa Rosa and San Jacinto Mountains National Monument.

UNESCO designated the Mojave and Colorado Deserts Biosphere Reserve in 1984, grouping four management units: Death Valley National Park, Joshua Tree National Park, the Santa Rosa Mountains Wildlife Management Area and Anza-Borrego Desert State Park. Its boundaries later became unclear after Death Valley National Monument was expanded and reorganized into a national park, and the Santa Rosa Mountains area became part of the Santa Rosa and San Jacinto Mountains National Monument. Little has been published about the reserve since, though interest rose in 2008 with proposals for human use in Anza-Borrego.

The reserve's name comes from the Mojave and Colorado deserts it spans, with Death Valley as its principal feature. Its four founding units were Death Valley National Park, Joshua Tree National Park, the Santa Rosa Mountains Wildlife Management Area and Anza-Borrego Desert State Park. Little has been published about the reserve since 1984, and interest rose in 2008 with proposals for human activity in Anza-Borrego.

Visit between October and April when temperatures are more bearable and the sun less intense across these areas. Bring plenty of water since freshwater is scarce throughout much of the reserve and the dryness is extreme.

The reserve's boundaries are no longer clear: Death Valley National Monument was later enlarged and reorganised as Death Valley National Park, and the Santa Rosa Mountains Wildlife Management Area became part of the Santa Rosa and San Jacinto Mountains National Monument. Little has been published about the reserve since 1984, and it was largely overlooked until interest rose around 2008 with proposals for human activity in Anza-Borrego Desert State Park.