The Oregon High Desert is located in the southeast of the U.S. state of Oregon, east of the Cascade Range and south of the Blue Mountains. The desert covers most of five Oregon counties and averages 4,000 feet (1,200 m) in altitude. The northern region is part of the Columbia Plateau, where higher levels of rainfall allow the largest industry on private land to be the cultivation of alfalfa and hay. The southwest region is part of the Great Basin and the southeast is the lower Owyhee River watershed. The U.S. Bureau of Land Management owns most of the region's public land and manages more than 30,000 square miles (78,000 km²)^{[not verified in body]} including five rivers designated as Wild and Scenic.

Compared to Western Oregon, the high desert is arid, averaging 15 inches (380 mm) of annual rainfall. Contrary to its name, most of the high desert is not dry enough to truly qualify as desert, and biologically, most of the region is classified as shrubland or steppe.

At 9,733 ft (2,967 m) above sea level, the summit of Steens Mountain is the highest point in the high desert. The broad fault-block mountain is characteristic of the basin and range plate tectonics of the high desert. About 16 million years ago, during the early Miocene epoch, lava flows from volcanic eruptions covered about half the surface area of Oregon. The Earth's crust then began stretching, giving way to further volcanic activity from 15 million to 2 million years ago. Several ice ages over this time formed the large lakes in the high desert.

The climate of the high desert provides habitat for mammals such as pronghorn, coyote, mule deer, black-tailed jackrabbit, and cougar. Birds common in the region include sage-grouse, California quail, and prairie falcon. The western juniper is the most common tree in the region, and big sagebrush and common woolly sunflower are the region's most widespread plants.

The high desert of Oregon is located in the central and southeastern parts of the state. It covers approximately 24,000 square miles (62,000 km²), extending approximately 200 miles (320 km) from central Oregon east to the Idaho border and 130 mi (210 km) from central Oregon south to the Nevada border. Most of the region is located in Crook, Deschutes, Harney, Lake, and Malheur counties.

The high desert is named as such for its generally high elevation, averaging about 4,000 feet (1,200 m) across the region. It is bordered by the eastern foothills of the Cascade Range to the west. The Blue Mountains are the geographical boundary to the north, marking the northern end of the high desert's semi-arid plateau. The southern high desert is part of North America's Basin and Range Province, which extends south through Nevada and Arizona and into Mexico. It contains large alkali lakes and tall cliffs, some with a prominence of more than 2,000 ft (610 m). Steens Mountain, in Harney County, is the highest point within the region; its summit is 9,733 ft (2,967 m) above sea level. To the east, the high desert country of the Columbia Plateau extends across the Snake River and into Idaho.

A number of rivers flow through the high desert region. These include the Deschutes River and its tributary the Crooked River, as well as the Malheur, Owyhee, and John Day rivers, which are all within the Columbia River watershed. Because the high desert encompasses the portion of the hydrographic Great Basin located in Oregon, smaller rivers in the high desert flow into closed basins. The Chewaucan River, the Donner und Blitzen River, and the Silvies River each flow into some of the high desert's salt lakes.

The largest landowner in eastern Oregon is the U.S. government. The Bureau of Land Management administers over 13.6 million acres (55,000 km²) in the bureau's Burns, Lakeview, Prineville, and Vale districts, most of which are in the state's high desert country. In addition, Congress has designated specific sections of the Crooked, Deschutes, Donner und Blitzen, Malheur, and Owyhee rivers as part of the National Wild and Scenic Rivers System.