Long Valley-Lake County is an American Viticultural Area (AVA) located in the eastern part of Lake County, California, established in April 2023 and encompassing 7,605 acres (30.78 km).

A transverse valley sitting on a geologic formation known as the Cache Formation, its floor is at 1,322 feet (403 m) above sea level, with foothills rising another 200 to 500 feet. Lake deposits form a soil composed of "tuffaceous and diatomaceous sands and silts, limestone, gravel, and intercalated volcanic rocks". Categorized as a Region III on the Winkler scale, Long Valley's annual recorded rainfall is similar to other Lake County AVAs, between 27 inches (690 mm) and 33 inches (840 mm), increasing as one moves west.

During the growing season, winds blowing through the valley cool the vines from the heat of the day. Cool air drainage provides protection from damaging late spring frosts in vineyards in the foothills, while vineyards along the valley floor require overhead sprinklers for protection.

The petition for the Long Valley AVA also requested an expansion of the boundaries of High Valley AVA, which Long Valley borders to the southwest, in order to close a gap, and a modification of the North Coast AVA in order to fully encompass the new AVA. The TTB agreed to those boundary changes.

Cache Creek Vineyards, which is based at the southern tip of Long Valley, and Shannon Family of Wines, which in 2015 acquired 280 acres in the area, were key petitioners to get the region recognized as an American Viticultural Area.

As of May 2024, three wineries operate within the Long Valley boundaries: Noggle Vineyards & Winery, Cache Creek Vineyards, and Stonehouse Cellars.

39°03′55″N 122°35′30″W / 39.0652°N 122.5917°W / 39.0652; -122.5917