The Old Vic's next season runs from September until July 2005. The seven-figure deal will see Morgan Stanley branding appear on posters, programmes and other publicity material. Branding will appear in the venue itself from September.
Spacey became artistic director of the Old Vic last year, and directs and acts for the theatre.
In the past Morgan Stanley has sponsored arts events including exhibitions at Tate Britain and the opening of Somerset House.
In March the US investment bank appointed former Egg marketer Patrick Muir as its first vice-president and head of marketing for its consumer banking group (Marketing, 4 March).