The RHS Chelsea Flower Show, formally known as the Great Spring Show, is a garden show held for five days in May by the Royal Horticultural Society (RHS) in the grounds of the Royal Hospital Chelsea in Chelsea, London. Held at Chelsea since 1912, it is the most famous flower and landscape gardens show in the United Kingdom, and perhaps in the world. The show is attended by members of the British Royal Family and attracts visitors from all continents.

Highlights to the Chelsea Flower Show include the avant-garde show gardens designed by leading names with Floral Marquee at the centrepiece. The Show also features smaller gardens such as the Artisan and Urban Gardens.

The Chelsea Flower Show receives a lot of publicity. 157,000 visitors attend the show each year (number limited by the capacity of the 11-acre (45,000 m2) ground), and all tickets must be purchased in advance. From 2005 the show was increased from four days to five, with the first two days only open to RHS members. The show is extensively covered on television by the BBC. Several members of the British Royal Family attend preview of the show, as part of the royal patronage of the RHS. The area of land devoted to show gardens increased steadily between 1970 and 2000 and the show has become an important venue for watching trends. New plants are often launched at the show and the popularity of older varieties revived under the focus of the horticultural world. It is the garden design equivalent of a catwalk at a fashion show.