They'll be raising money for the Democratic Party of Wisconsin with a script read of the 1987 cult classic.
People who donate will get an invitation to a live stream of the performance.
If you wish, the live stream will be available for donations of any amount but will only be shown once.
Among those involved include Cary Elwes, Robin Wright, Carol Kane, Chris Sarandon, Mandy Pantinkin, Wallace Shawn and Billy Crystal.
Director Rob Reiner is also taking part in the reunion.
Patton Oswald will moderate a question and answer session on September 13 at 6 p.m.