Guerneville (/ˈɡɜːrnvɪl, -nivɪl/) is an unincorporated community and census-designated place in the Russian River Valley of Sonoma County, California, United States.

Redwoods grew in the riverbed with such vigor that just a few centuries ago, the valley had the greatest biomass density on the planet, according to local lore.

[citation needed] The local Pomo Indians had long used the area as a summer camp and called it "Ceola" (/ˈsiːoʊleɪ/ or cee-oh-lay) which meant "shady place."

A large stand of ancient trees is preserved in the Fife Creek watershed, now the centerpiece of Armstrong Woods Park.

The present name Guerneville was introduced to honor Swiss immigrant George Guerne, a local businessman of the 19th century who owned the town's sawmill.

[7] The extensive redwood forests on the surrounding mountains are less than 200 years old, having been replacement plantings for much of the logging done in the 19th century.

In the late 19th century, the area became popular with wealthy vacationers from San Francisco and surrounding communities.

A renaissance took place in the late 1970s as numerous gay entrepreneurs from San Francisco identified the area as a prime recreational destination for weekends.

Guerneville is located in western Sonoma County, along the Russian River on State Route 116, between Monte Rio to the west and Forestville to the east.

[1] Guerneville has cool, wet winters and warm, dry summers, a climate typical of northern coastal California.

The associated condensation creates "fog drip," which sustains the numerous redwood trees, ferns, and other vegetation.

Other nearby cooperative National Weather Service stations are in Occidental, Cazadero, and Fort Ross.

Guerneville is an LGBTQ+ vacation destination, and hosts an annual Russian River Pride Parade and Celebration.

Places of interest include Armstrong Redwoods State Natural Reserve and the adjacent Austin Creek State Recreation Area, the Russian River with its meandering flow and wildlife, Johnson's Beach, which hosted the Russian River Jazz and Blues festival In the past and provides summer swimming and boating, and the close proximity of the Pacific Ocean.

[26] Guerneville/lower Russian River events receive daily coverage by the Santa Rosa Press Democrat's "hyperlocal" online Towns section.

The Russian River area occasionally appears in local and/or national news due to significant winter flooding, the worst of which occurred in 1986.

Because much of the housing is elevated, thanks in large part to FEMA grants, floods no longer have the impact they once did and recovery for most residents and businesses is much faster than in earlier times.

The effects of floods are mitigated by the extensive upstream floodplain storage capacity of the Laguna de Santa Rosa.