The fire, reported shortly before 5 p.m., started in rugged and steep terrain in the Woodacre area above Deer Park School, according to Battalion Chief Mike Giannini.
Firefighters had to deploy more than 3,000 feet of hose to supply water to the fire scene. A total of 81 personnel from the Marin County Fire Department, Ross Valley Fire Department and Cal Fire were involved in fighting the flames, along with three water dropping airplanes and one helicopter.
The fire was contained at 8 p.m.
Giannini said the area where the fire occurred, part of the Mt. Tamalpais watershed, has been plagued by Sudden Oak Death, a disease known to kill oaks and other plants in the western United States.
No structures were threatened by the fire and no injuries were reported. The cause of the fire remains under investigation.