José Joaquín Estudillo was a Californio statesman and ranchero who served as the 2nd Alcalde of San Francisco. A member of the prominent Estudillo family of California, he is also considered the founder of the city of San Leandro.

The Estudillo family is a prominent Californio family of Southern California. Members of the family held extensive ranchos and numerous important positions, including California State Treasurer, Mayor of San Diego, and Commandant of the Presidio of San Diego.