The Acjachemen (/ɑːˈxɑːtʃəməm/, alternate spelling: Acagchemem) are an Indigenous people of California. They historically lived south of what is known as the Aliso creek and what became San Diego counties. Their language was a variety closely related to the Luiseño language of the nearby Payómkawichum (Luiseño) people. In the 20th century, the Juaneño Band of Mission Indians, Acjachemen Nation was organized but is not federally recognized. The lack of federal recognition has prevented the Acjachemen from accessing, protecting, and restoring their ancestral lands and sacred sites.