Tom Hoblyn will create a show garden for Arthritis Research UK in his fifth year at Chelsea. The charity's debut will feature a garden inspired by the Renaissance gardens of Italy.
Hoblyn's design is based on gardens at Villa Lante and Villa d'Este and will focus on water features among formal Mediterranean planting.
Jo Thompson, who won a certificate of merit at this year's event, is to design a Staycation Garden for the Caravan Club.
A metal caravan, named Doris and believed to be the first to feature in a Chelsea garden, will form the heart of a "blowsey" garden with roses, peonies, a dog kennel, hammock and undulating seats.
Other designers who have confirmed projects at next year's show include Andy Sturgeon and Arne Maynard, who is designing for Laurent Perrier. Chris Beardshaw will work with students from learning disability charity Furzey Gardens.
Two members of the Olympic Park design team have also confirmed show gardens at the event. Nigel Dunnett will create a Blue Water Garden for Royal Bank of Canada, while Sarah Price is designing a garden for The Daily Telegraph.