This article is about the volcanoes in Oregon. For other meanings, please see Three Sisters (disambiguation).

Three Sisters
Elevation:	South Sister --- 10,363 ft (3,158 m)
Latitude:	South Sister --- 44° 6′ 12.58″ N
Longitude:	South Sister --- 121° 46′ 9.35″ W
Location:	Oregon, USA
Topo map:	USGS South Sister
Range:	Cascades
Type:	Stratovolcano/Shield volcano cluster
Age of rock:	Quaternary
Easiest route:	hike up South Sister

The Three Sisters are three volcanic peaks of the Cascade Range, located near the town of Sisters, Oregon.

The North Sister is oldest, with towering rock pinnacles and brilliant glaciers. It has not erupted since the late Pleistocene. It is the most dangerous climb of the Three Sisters, due to its level of erosion, and thus rockfall.

The Middle Sister is the smallest and most poorly studied. It is the second youngest. No reports on its potential for eruptions can be made.

The South Sister is the youngest and tallest volcano of the trio. It last erupted about 1600 years ago. It has a well developed crater, which is covered by a glaciated lake. It is a long, steep, non-technical hike that can be easily completed in a day by reasonably-fit hikers. Popular starting points are the Green Lakes or Devil's Lake trailheads.

In 2000, a satellite discovered that there was a deforming uplift near the South Sister. This could mean that she is awakening. Depending on the type, the eruption could either result in quiet emissions of lava, the town being buried, or even a total levelling of the mountain.

At about 10:00 AM PST on Tuesday, March 23, 2004, an earthquake swarm began with epicenters in the area of uplift. The hundreds of small earthquakes subsided over several days. Scientists at the U.S. Geological Survey had been expecting such earthquake swarms to accompany the uplift, and they are not considered precursory events to an eruption.

The Sisters were named Faith, Hope, and Charity by early settlers.

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