Lake County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 8,160. Its county seat is Lakeview. The county is named after the many lakes found within its boundaries, including Lake Abert, Summer Lake, Hart Lake, and Goose Lake.

Lake County is in the high desert region known as the Oregon Outback, on the northwestern edge of the Great Basin. The county is generally divided between the communities around Lakeview and Paisley to the south and the communities around Christmas Valley, Fort Rock, and Silver Lake to the north.

Its economy consists largely of agriculture and natural resource management and extraction. It is home to many large cattle ranches, hay farms, and timber holdings (both public and private), as well as several frontier towns and early 20th-century homesteads. Although lumber was once a primary economic driver in Lake County, today only one mill remains, at Lakeview.

Pre-Clovis era coprolites found in the Paisley Caves in northern Lake County in 2007 have been radiocarbon dated to 14,300 calendar years before present. DNA extracted from these human remains bears certain genetic markers found only in Native American populations. Luther Cressman found prehistoric artifacts in the Fort Rock Caves of northern Lake County in 1938, including basketry, stone tools, and a cache of woven sagebrush bark sandals which have been dated to more than 10,000 years ago.

European traders, explorers and military expeditions arrived in the region during the early part of the 19th century. Peter Skene Ogden led Hudson's Bay Company trappers to Goose Lake in 1827. In 1832, the Hudson Bay trappers under John Work were in the Goose Lake Valley and their journals mentioned Hunter's Hot Springs. Work's expedition visited Warner Lakes and Lake Abert and camped at Crooked Creek in the Chandler Park area. There they documented eating wild plums, which still grow in the area. They also reported being attacked by Indians. In 1838, Colonel J. J. Abert, a U.S. engineer, prepared a map that includes Warner Lakes and other natural features using information from the Hudson Bay trappers. In 1843, John C. Fremont led a party which named Christmas (Hart) Lake.

Lake County once hosted significant populations of Basque and Irish sheepherders. Disputes over grazing rights, exacerbated by the introduction of wheat farming, led to the eruption of range wars between cattle ranchers and sheep herders. At least one band of masked rifle-armed cattlemen killed sheep in the northern part of the county and in Deschutes County during the early 20th century and they came to be known as "sheepshooters". According to the Oregon History Project, 2,300 sheep were killed in a single night in April 1904 in Lake County.

Lake County grew with the arrival of homesteaders, but the dry climate made for challenging development.

Lake County was created from Jackson and Wasco Counties on October 24, 1874, by the State Legislature. It then included the present Klamath County and all of the present Lake County except Warner Valley. In 1882, land was assigned to create Klamath County, and in 1885 the Warner area from Grant County was added. Linkville, now Klamath Falls, was the first county seat.