Mount Saint Helena, Mountain peak in Mayacamas Mountains, California.

Mount Saint Helena is a peak in the Mayacamas Mountains whose flanks lie in Napa, Sonoma and Lake counties. It has five summits arranged in a rough M shape; North Peak, in Sonoma County, is the highest, and the second-tallest, just east of it, is the highest point in Napa County. The mountain is built of uplifted volcanic rock from the Clear Lake Volcanic Field, about 2.4 million years old.

The Wappo called it Kanamota, "Human Mountain"; Spanish colonists renamed it Mount Mayacamas. A Russian survey party that climbed the peak in 1841 left a copper plate on the summit inscribed with the date and the name of Princess Helena de Gagarin, wife of Fort Ross commander Alexander Rotchev. That plate gave the mountain its present name.

The Wappo called the peak Kanamota, "Human Mountain". Spanish colonists renamed it Mount Mayacamas, and in 1841 a Russian survey party gave it its current name after Princess Helena de Gagarin, wife of Fort Ross commander Alexander Rotchev. Ursula K. Le Guin's novel Always Coming Home features a post-apocalyptic society that considers Mount Saint Helena sacred.

Trails to the summit leave from Robert Louis Stevenson State Park and run about 6 miles (9.7 km). The route crosses slopes of volcanic rock, and the upper section is exposed, with snow possible in winter on one of the few Bay Area peaks that gets it.

The Napa River begins on the southeast slope of Mount Saint Helena. The mountain's five summits form a rough M, and the second-highest, just east of the main peak, is the highest point in Napa County. The Wappo name Kanamota means "Human Mountain".