The Mexican Secularization Act of 1833, officially called the Decree for the Secularization of the Missions of California, was an act passed by the Congress of the Union of the First Mexican Republic which secularized the Californian missions. The act nationalized the missions, transferring their ownership from the Franciscan Order of the Catholic Church to the Mexican authorities.

Indigenous peoples of California, commonly known as Indigenous Californians or Native Californians, are a diverse group of nations and peoples that are indigenous to the geographic area within the current boundaries of California before and after European colonization. There are currently 109 federally recognized tribes in the state and over forty self-identified tribes or tribal bands that have applied for federal recognition. California has the second-largest Native American population in the United States.