The Blithewold Mansion, Gardens and Arboretum is an arboretum of 13 ha (33 acres), located mid-way between Newport and Providence, Rhode Island, on Bristol Harbor with views over Narragansett Bay. It includes a mansion, with a 4 ha (10 acre) lawn and nearly 300 species of woody plants in its arboretum and gardens, including both native and exotic species.

The Mansion and its grounds were established in the 1890s by Augustus and Bessie VanWickle as their summer retreat. Augustus VanWickle was from Hazleton, Pennsylvania, with a fortune in the coal-mining business. Today's grounds are primarily the design of John DeWolf, and date between 1896 and 1913.

Blithwold's grounds include species from North America, Europe, China and Japan. Specimen trees include magnolia (Magnolia spp.), linden (Tilia spp.), Ginkgo (Ginkgo biloba), Black Tupelo (Nyssa sylvatica), Dawn Redwood (Metasequoia glyptostroboides), Franklinia (Franklinia alatamaha), Eastern Hemlock (Tsuga canadensis), various oaks (Quercus spp.) and beeches (Fagus spp.). Other notable trees include a weeping Pagoda Tree (Styphnolobium japonicum 'Pendula'), Hiba (Thujopsis dolobrata), Katsura (Cercidiphyllum japonicum), and Sugi (Cryptomeria japonica). The grounds also include English Yews (Taxus baccata) and Eastern Junipers (Juniperus virginiana), as well as what is claimed to be the largest Giant Sequoia (Sequoiadendron giganteum) on the East Coast, planted in 1911.

Blithewold's Bamboo Grove covers an area nearly the size of a tennis court, and is planted with Phyllostachys aureosulcata, the Yellow-groove bamboo, which grows to 10 m (30 feet) tall.

Blithewold has maintained contacts with the Arnold Arboretum ever since 1926, when staff botanists visited Blithewold to see the Chinese toon tree (Toona sinensis) in flower for what was believed to be the first time in the United States.