Elijah Wood, the Hobbit Frodo in Peter Jackson's $360 million film project, will contest a celebrity bath tub race at the Wellington Dragon Boat Festival.
Other Rings stars will be Dominic Monaghan and Billy Boyd, who play the hobbits Merry and Pippin, and Orlando Bloom, who plays the elf Legolas.
Participants and spectators alike will be asked for $5, with proceeds going to Ronald McDonald House.
The race on Wellington Harbour will be held between noon and 1pm.
Festival director Annette Cullen said the best viewing spot would be next to Shed 6, behind the Queens Wharf Events Centre.
"We feel quite honoured that they ( the film's stars ) have wanted to play," she said. Other celebrity participants include the Capital Shakers netball team.