Michael Park, co-driver for Markko Martin, has died after an accident on stage 15 of Wales Rally GB on Sunday.
Park, 39, was killed when Martin's Peugeot 307 crashed heavily into a tree on the passenger's side during the 17-mile Margam stage.
Estonian Martin escaped unhurt. The stage was halted and organisers then decided to cancel the final two stages.
Petter Solberg won the event after Sebastien Loeb declined to retain his world title in such circumstances.
A statement from the organisers said: "It is with deep regret that we confirm that Michael Park was fatally injured following an accident on special stage 15.
"The next of kin has been informed. The driver of car number eight, Markko Martin, is uninjured."
No spectators were involved in the accident.
Park, nicknamed 'Beef', was a highly-experienced co-driver who had worked with former champions Richard Burns and Colin McRae.
Married with children, he first began rallying on the world championship circuit in 1994 as Mark Higgins' co-driver.
Park, from Newent in Gloucestershire, teamed up with Martin in 2000 when the Estonian was rallying a privately-entered Toyota.
They stayed together at Subaru and Ford before moving to Peugeot this year. The pair had won five world rallies together.
Peugeot issued a statement confirming that Martin had hit a tree on the right hand side of the car, fatally injuring Park.
"Peugeot Automobiles and Peugeot Sport would like to express their feeling of extreme sadness and deep emotion to the family of Michael Park."
The cancellation of the remaining stages and withdrawal of Peugeot's Marcus Gronholm after Park's death would have meant Citroen's Loeb retaining his world title.
But the Frenchman declined to win the title in that manner and deliberately incurred a two minute penalty before heading back to Cardiff for the offical finish.
That left him in third place with Subaru's Solberg declared the winner and Citroen's Francois Duval runner-up.
The rally finished at a sombre Millennium Stadium, where flags flew at half mast and a minute's silence was observed.