Mahnke Peak is a 3,652-foot mountain in the Mayacamas Mountains of northern California, in Mendocino County near the Lake County line. In a warm-summer Mediterranean climate, it stands with 612 feet of prominence and broad summit views toward the power plants of The Geysers geothermal field. The peak was named for John Christian Christof Mahnke and his family, who grazed several hundred angora goats on the mountain for 70 years. It also marks the western edge of the Russian River watershed, with Hoil Creek and Hummingbird Creek draining from its slopes through separate tributary systems that both ultimately reach the Russian River.