Peter O'Toole, Sir Ian McKellen, Timothy West and Prunella Scales were among the stars supporting the Rose Theatre's appeal launch on Tuesday night.
The champagne party was held on the Rose Theatre site in Park Street to hear the Rose Theatre Trust chairman Harvey Sheldon announce a drive to raise £4m for a full excavation of the site.
It is hoped to excavate for the first time the eastern side of the theatre and maybe undertake further digging on the section examined in 1989.
The eventual plan is to leave the majority of the theatre's remains preserved in situ with the entire site open to the public.
Monies provided by the developers of Rose Court, which was controversially built spanning the site, are being released and an approach is also being made to the Heritage Lottery Fund. Meanwhile the Trust, which had six sponsors for its appeal launch, is looking for sponsors of signage, events and publicity.
Financial Times Chairman Sir David Bell welcomed the guests who included the Lord Mayor of London Alderman Michael Savory and historian Dan Cruikshank.
• The wooden Rose Theatre was built in 1587 alongside a farm track, now Park Street, on the Bishop of Winchester's estate. Plays by Ben Jonson, Christopher Marlowe and William Shakespeare were performed on the stage.