Middletown is a census-designated place (CDP) in Lake County, California, United States.

Middletown was given its name because it is halfway between Lower Lake and Calistoga, which is 17 miles (27 km) to the south.

At one time, the community was known as Middle Station, and was a halfway point on the stagecoach route over Mt.

[3] Middletown enjoyed a robust quicksilver (mercury) mining industry through the end of the 19th century.

By the early 1900s, cattle and sheep ranching were prominent, along with some limited pear and walnut production.

In the 1970s and early 1980s, exploitation of nearby geothermal energy resources brought an influx of workers into the local economy.

As housing prices in the Bay Area increased in the late 20th century, Middletown and nearby Hidden Valley Lake enjoyed a population boom as commuters moved to the Middletown area looking for affordable housing.

Nearby tourism includes Harbin Hot Springs and the Twin Pine Casino located on the local Rancheria south of the town.

A large resort, 2 miles (3.2 km) southeast of town, was proposed in 2020, consisting of low-density residential development, preserved open space, retail space, restaurants, and several boutique hotels.

[4] In the late afternoon and early evening hours of September 12, 2015, about half the town, including city blocks, commercial buildings and an apartment complex, was destroyed by the fast-moving Valley Fire.

[5] The town was directly in the path of the advancing fire, and suffered a "devastating blow".

[1] According to the United States Census Bureau, the CDP has a total area of 1.8 square miles (4.7 km2), all of it land.

[16] The Middletown Rancheria, an Indian reservation of Pomo, Lake Miwok, Wappo, and Wintu, is located just south of town and is home to a tribal casino as well as a tribal gas station which brings in people from around the area for its low prices.

In the California State Legislature, Middletown is in the 2nd Senate District, represented by Democrat Mike McGuire, and in the 4th Assembly District, represented by Democrat Cecilia Aguiar-Curry.