Diamond Peak Wilderness, Protected natural area in Oregon, United States.

Diamond Peak Wilderness is a 52,337-acre (21,180 ha) protected area in Oregon straddling the Cascade crest within the Willamette and Deschutes National Forests. It is centred on the 8,744-foot (2,665 m) shield volcano Diamond Peak, whose glaciers left snowfields near the summit and dozens of small lakes, from 1 to 28 acres, around the peak. About 14 miles (23 km) of the Pacific Crest Trail cross the wilderness, and some 52 miles (84 km) of trails run through it.

The Forest Service designated the Diamond Peak Wild Area on February 5, 1957, covering 36,637 acres. The 1964 Wilderness Act reclassified it as wilderness, and the Oregon Wilderness Act of 1984 enlarged it to its present 52,337 acres.

Visitors come to experience terrain without motorized vehicles or commercial facilities, seeking the sounds and solitude of untouched mountain landscapes. This protected setting allows people to connect with nature on a quieter level.

Good footwear is essential since trails cross rocky terrain and steep slopes, especially at higher elevations. Summer through early fall offers the best conditions for hiking when snow has melted and paths are accessible.

Diamond Peak is a shield volcano, and glaciers later carved its bulk; when they receded, dozens of small lakes remained around the mountain, ranging from 1 to 28 acres. Marie Lake, Divide Lake and Rockpile Lake serve as base camps for the summit climb.