Sir Owen Glenn is donating $3 million to the restoration of Rotorua's Sir Howard Morrison Performing Arts Centre.
The centre was closed in November after it fell below earthquake standards.
Sir Owen, 77, a close friend of the late entertainer, said he was making the donation "as a gesture of friendship in memory of Howard, and somewhere for music and culture to blossom in Rotorua".
He had not yet seen plans for a proposed refurbishment but would do so when he visits Rotorua later this month, where he is to be welcomed at Ohinemutu village to thank him for his contribution.
Rotorua mayor Steve Chadwick said Sir Owen's offer to help was "absolutely fantastic". "It's just amazing generosity."
The donation was a huge boost to the upgrade - which could cost up to $12m if one upper-end option including upgrading the concert chamber, foyer and banquet room, plus the required earthquake strengthening – was accepted. Earthquake strengthening alone has been estimated at up to $4m.
Having Sir Owen as a cornerstone investor allowed the council to seek other funding, Chadwick said.
"That allows us to go out to other partners and say, Sir Owen Glenn's given $3m. Can you look at some funding support too."
Chadwick said the closure of the centre was devastating.
"We lost a key facility in Rotorua, and we've really felt the pinch in a very busy… [and] a very creative centre, so we've had to move events everywhere."
She hoped a proposed restoration could be completed this year. "We can't be without a facility like this long term, so there is a degree of urgency in terms of settling on a solution and getting things underway."
As well as being a top tourism destination, Rotorua has been named as one of the top places to see in 2018 in the prestigious The New York Times' Places to Visit list – it was known for hosting cultural events.
Rotorua businessman and arts supporter Brett Marvelly has been helping the Rotorua Lakes Council in the proposed restoration of the Sir Howard Morrison Performing Arts Centre, including seeking funding for its refurbishment.
Sir Owen's donation was "fantastic - so generous, and so needed", he said. "We're a community which is very, very performance orientated. The theatre is really utilised a lot."
The performing arts centre was closed after a detailed seismic assessment had found the building had fallen below building standards and was earthquake-prone.
The cost for the earthquake repairs should be known by April. An early estimate was $2.7m-$4m. The council had funding for earthquake strengthening in its long-term plan.
Sir Owen's $3m donation would not be used for seismic repairs but for the centre's refurbishment.
A proposed upgraded concert theatre, with a planned up to 250-300 seat capacity, would feature "sound and lighting right up to television standards, and we're also probably looking at putting in a recording studio in it as well".
A possible expansion of the Civic Theatre's seating capacity from 686 to 1000 could be considered later.
Sir Howard Morrison's legacy would continue at the performing arts centre, and his family had been included in plans for the proposed restoration.
Marvelly met Sir Owen and the late Sir Howard through the musical career of his daughter - singer/songwriter Lizzie Marvelly – who "feels really strongly" about the performing arts centre.
Sir Owen today opens up about his philanthropy and ongoing battle with cancer in a feature in the Herald on Sunday. He estimates he has given away more than $50m to charity, and is pledging that a "substantial" chunk of his estimated $400m fortune will be donated after his death.