The Sir Harold Hillier Gardens, Romsey is an arboretum comprising 72 hectares accommodating over 42,000 trees and shrubs in about 12,000 taxa, notably a collection of oaks, camellia, magnolia and rhododendron.
The Gardens are located 5 km north-east of the town of Romsey in Hampshire, England, and were formerly known simply as the Hillier Arboretum, founded by nurseryman Harold Hillier in June 1953 when he acquired Jermyns House and its grounds. The arboretum was given to Hampshire County Council in 1977 to be managed as a charitable trust. Sir Harold Hillier was knighted in 1983, just two years before his death at age 80 in 1985. The gardens were added to the Register of Parks and Gardens of special historic interest in England in 1997.