Eugene O'Neill National Historic Site, National Historic Site in Contra Costa County, United States.

Eugene O'Neill National Historic Site preserves Tao House, a two-story, three-bedroom Monterey Colonial home that Eugene O'Neill and Carlotta Monterey designed themselves on a hillside above Danville. Its dark blue ceilings represent the sky and dark wood floors the earth, with Noh masks, Chinese guardian statues and lacquerware inside. The grounds cover 13 acres (5.3 ha).

Eugene O'Neill used his 1936 Nobel Prize money to build Tao House, where he lived from 1937 to 1944. The house was listed on the National Register of Historic Places on May 6, 1971, and designated a National Historic Landmark on July 17, 1971. It became a National Historic Site on October 12, 1976, and passed to the National Park Service on June 12, 1980.

The house is named Tao House, reflecting the playwright's deep connection to Eastern philosophy. Visitors can see today how these ideas shaped the rooms through the chosen decorations and the way the building was designed.

Access is by reservation only, and private vehicles cannot reach the house; a free shuttle leaves Danville twice daily at 10am and noon, Wednesday to Sunday, with an extra 2pm run on Saturdays. Saturday tours are self-guided and need no booking. Trails from Las Trampas Regional Wilderness also lead to the site, though reservations are advised for walkers and riders.

The interior displays traditional Noh masks and Chinese guardian statues that show how deeply the resident was inspired by Eastern aesthetics. This collection was more than decoration—it reflected his artistic thinking.