Prince William and Kate will go head to head in the King's Cup Regatta in August, staged in the waters off the Isle of Wight, to raise awareness and funds for eight of their patronages.
The couple will launch the event at the Cutty Sark on Tuesday, the famous tea clipper ship in Greenwich, south-east London, and will be joined by children and young people from a number of their chosen charities.
The regatta will be hosted by William and Kate on August 9 on the Isle of Wight, and will see the couple compete as the skippers of rival boats, part of an eight-strong field.
The winning team will be awarded the King's Cup, a historic trophy first presented by King George V at Cowes' Royal Yacht Squadron in 1920.
William and Kate hope the King's Cup will become an annual event, bringing greater awareness to the wider benefits of sport, while also raising support and funds for their causes.
The duke trounced his wife when they competed in a dragon boat race in Canada in 2011, but Kate got her revenge three years later when she won a sailing event in Auckland during their tour of New Zealand.
William took the honours again during a visit to the German city of Heidelberg in 2017, when he was victorious in a riverboat race against his wife.
The eight boats taking part in the King's Cup will each represent one of the charities that are being supported this year by the royal couple.
These include Child Bereavement UK, Centrepoint, the London Air Ambulance Charity 30th Anniversary Campaign, and Tusk - four causes which the duke supports as patron.
The duchess will support four of her patronages: Action on Addiction, Place2Be, the Anna Freud National Centre for Children and Families, and The Royal Foundation in connection with her work on the early years development of children.
Members of the public can watch the race from the SailGP Race Village along the Cowes foreshore, which is free to access and will include an 800-seater grandstand.
Footage from the race will play on screens across the town and there will be a number of family-friendly activities and exhibits to promote sailing around the event, including initiatives and programmes for children and young people.