Santiago Argüello (1791–1862) was a Californio, a soldier in the Spanish army of the Viceroyalty of New Spain in Las Californias, a major Mexican land grant ranchos owner, and part of an influential family in Mexican Alta California and post-statehood California.
Santiago Argüello was born in Monterey, Las Californias Province of New Spain. He was the son of: José Darío Argüello - a soldier, pioneer in Las Californias, founder of Pueblo de Los Angeles (Los Angeles), twice a Spanish colonial governor (of Alta California and of Baja California); and María Ignacia Moraga - a niece of José Joaquín Moraga, the founder of Pueblo de San José (San Jose). His brother was Luis Antonio Argüello, California's first native-born governor, in office 1822–1825 as Mexican Alta California governor.
Argüello married María del Pilar Ortega in Santa Barbara in 1810, the granddaughter of José Francisco Ortega - Commandant of the Presidios of San Diego, Santa Barbara, Monterey, and Loreto. They had fifteen children together, five in Santa Barbara and ten in San Diego.
Argüello was tall and stout. His fair complexion and black hair, along with his distinguished manner gave him a 'regal' presence, though his reserved manners caused some to dislike him. He was a man of ability and left an 'honorable' record.