Headwaters Forest Reserve, Nature reserve in Humboldt County, United States.

Headwaters Forest Reserve is a nature reserve in Northern California that protects stands of old-growth coastal redwoods, younger recovering forest, and watershed areas near Humboldt Bay. A trail runs through the property, passing through different forest types and eventually reaching the most ancient grove at its heart.

The land was logged for decades by timber companies, and the fight to protect its remaining old-growth trees became one of the most contested conservation battles in California during the 1990s. In 1999, federal and state agencies acquired the property, turning it into a protected reserve.

The reserve contains the site of Falk, a historic lumber mill town, including its mill site within the reserve boundaries. The town's remains are part of the landscape that visitors can pass, showing where a company settlement once stood beside the forest.

The main trail is open to hikers and cyclists on certain sections, but the full round trip is long enough to require good preparation and plenty of water. Weather in the forest can shift quickly, so layered clothing is a practical choice regardless of how the morning starts.

The reserve's name was coined in March 1987 by activist Greg King after a solo hike through Pacific Lumber's northern redwood holdings. The area later became the largest old-growth redwood stand protected as a result of the Redwood Summer protests.