A leading London-based businessman is donating £20m to the Royal Opera House and the Wales Millennium Centre.
The Wales Millennium Centre will open in November 2004
The money, which will establish a partnership between the two flagship organisations, is coming from South African Donald Gordon over five years.
It is one of the largest single private donations ever made to the performing arts in the UK, and could herald hands-on involvement from the multi-millionaire in arts projects around Britain.
The money will be divided equally between the two and will help meet the building costs of the Wales Millennium Centre, which is due to open in Cardiff Bay.
The £104m arts centre, situated in Cardiff Bay, will use £6m towards its construction, reducing the shortfall it needs from private funding to £2.7m.
The remaining £4m will be used to ensure excellence in programming and accessibility, such as subsidising ticket prices.
Welsh Secretary Peter Hain welcomed the news of the donation.
"It is a brilliant boost for what is an awesomely-impressive centre," he said.
The source of the money is a man ranked 51st in the Sunday Times's Rich List, which estimated his fortune at more than half a billion pounds.
Mr Gordon is a retail tycoon, whose main operation in the UK is Liberty International PLC, owner of some of Britain's biggest out-of-town shopping centres.
The arts, he said, had been a key part of his life since moving to the UK four years ago.
"This donation is made ahead of my retirement... and heralds the beginning of a fascinating new activity that will become an important and enjoyable focus of my life in retirement," he said.
In March this year, the Royal Opera House announced plans to widen its appeal and entice more diverse audiences.
The Royal Opera House will share the money
It has been screening live performances on big screens around the UK, and offering thousands of discounted tickets for productions.
The Wales Millennium Centre is expected to hold international musicals, operas, ballet and dance as well as becoming a home to the Welsh National Opera.
Internationally-renowned opera star Bryn Terfel will lead a glittering line-up of stars at the opening next year.
Stars including Charlotte Church, Matthew Rhys and Ruthie Henshall will also appear to launch the venue.
Earlier this year, the Welsh National Opera announced a programme of six wide-ranging new opera productions during the first 18 months of the centre.
The Welsh Assembly is investing £37m of public money in the centre, with £31m coming from the Millennium Commission, £10m from the Arts Council for Wales and £6m from the Welsh Development Agency.