Almost 10,000 people are expected to flood into Christchurch for the biggest sporting event the city's ever hosted.

The April 2018 Golden Oldies event gives keen sports people the chance to compete regardless of their age.

Christchurch's competition will mark the first time all sports have come together, rather than each sport having its own world event.

Christchurch & Canterbury Tourism spokeswoman Caroline Blanchfield said it will inject over $30 million into the economy.

"About 70,000 bed nights of accomodation would be about the number we're looking at, 70% of the athletes are coming from overseas for the event, so it's new money into the economy which is a great thing."

Blanchfield said the timing couldn't be better.

"So instead of having all our summer taken care of and being short of visitors in the low periods, we're going to have about 9000 people, plus the officials and supporters coming into our off-season."