Windsor Great Park is a Royal Park of 2,020 hectares (5,000 acres) to the south of the town of Windsor on the border of Berkshire and Surrey in England. It is adjacent to the private 265 hectares (650 acres) Home Park, which is nearer the castle. The park was, for many centuries, the private hunting ground of Windsor Castle, which dates primarily from the mid-13th century and still includes a deer park. Historically the park covered an area many times the current size known as Windsor Forest, Windsor Royal Park or its current name. The park is managed and funded by the Crown Estate, and is the only royal park not managed by The Royal Parks. Most parts of the park are open to the public, free of charge, from dawn to dusk, although there is a charge to enter Savill Garden.

Except for a brief period of privatisation by Oliver Cromwell to pay for the English Civil War, the area remained the personal property of the monarch until the reign of George III when control over all Crown lands was handed over to Parliament. The Park is owned and administered by the Crown Estate, a public body established by Act of Parliament in which the monarch and family members associated with its particular parts have non-executive, advisory roles. The park is on the Register of Historic Parks and Gardens with a Grade I listing. Windsor Forest and Great Park is a Site of Special Scientific Interest. Windsor Great Park is a nationally important site for fungi. Over 1,000 species have been found on the park's territory, including 43 species confined exclusively to Windsor. Several of Britain's rarest and most endangered species of fungi occur on the park's territory.