Plum Orchard, Historic house on Cumberland Island, St. Marys, United States.

Plum Orchard is a mansion on the western shore of Cumberland Island, Georgia, designed by Peabody and Stearns for George Lauder Carnegie and dedicated on October 6, 1898. The firm added wings in later years, probably in 1906. The house contains a rare squash tennis court.

Peabody and Stearns designed Plum Orchard for George Lauder Carnegie, a son of Thomas M. Carnegie, and it was formally dedicated on October 6, 1898. The firm added to the mansion in later years, probably in 1906. After Carnegie died, his widow Margaret Copley Thaw remarried and moved to Lake Naivasha, Kenya; most original furnishings were sold and pieces from Dungeness brought in. The Johnston family then occupied the house.

Plum Orchard was named for George Lauder, the Scottish industrialist uncle of George Lauder Carnegie, who commissioned the house. After Carnegie died, his widow Margaret Copley Thaw remarried and moved to Lake Naivasha, Kenya; most original furnishings were sold and pieces from Dungeness were brought in. The house was then occupied by the Johnston family, from Nancy Trovillo Carnegie Heaver Johnston's branch.

Plum Orchard sits on the western shore of Cumberland Island, reached by foot or bicycle from the Sea Camp dock about 7 miles south. The mansion is open to visitors only on ranger-led tours; the grounds and paths are unpaved and uneven in places.

Plum Orchard's mansion holds a rare squash tennis court, a court game distinct from modern squash. The source records the court as part of the house built for George Lauder Carnegie, dedicated on October 6, 1898. Visitors touring the estate can look for this surviving piece of the mansion's original recreational layout.