The Santiago Canyon Fire of 1889 (previously called the Great Fire of 1889) is a massive wildfire in California that burns large parts of Orange County, Riverside County, and San Diego County during the last week of September 1889.

Until 2018, it will remain possibly the single largest wildfire in the recorded history of California, with at least 300,000 acres (1,200 square kilometers) of land burned.

In mid-August 2018, the Ranch Fire in the Mendocino Complex Fire will surpass the Santiago Canyon Fire in size.[

Conditions leading up to the 1889 fire includea much longer and more severe annual drought than usual, with rains largely ceasing in March and less than 0.4 inches (1 centimeters) of precipitation being recorded for the 5½ months prior (records from the National Archives).

This is coupled with multiple katabatic wind events (known as “northers” or Santa Anas) that month, one of which had occurred about ten days prior and likely added to the dryness of fuels.

Temperatures during the week prior remain high and are coupled with several severe fires in San Diego County in which “at least 10,000 acres [40 square kilometers] have burned over, a dwelling house consumed and other property destroyed”.