The Santiam Fire was a very large wildfire that burned in Marion, Jefferson, Linn, and Clackamas counties, in northwest Oregon, United States.

Having ignited in August 2020, the 402,274-acre (162,795 ha) fire ravaged multiple communities in northwestern Oregon, before it was fully contained on December 10, 2020.

The first three fires gradually grew in size, before explosively spreading in early September during a heatwave, fanned by powerful east winds.

Initially, the three fires were unremarkable, being relatively small wildfires that smoldered in the rugged terrain of the Opal Creek and Mount Jefferson Wildernesses, within the Willamette National Forest.

[13] Early on September 8, the Lionshead and Beachie Creek Fires merged, probably at a point north of Detroit.

[12] On September 9, the Santiam Fire quickly moved into and destroyed the city of Detroit as it continued its westward spread.

[8][17] However, this fear subsided somewhat on the next day, as firefighters made progress on containing both the Santiam and Riverside Fires, with improved weather conditions.