Bell is the executive director of Pearson plc, the parent company of the Financial Times, and chairman of the Financial Times Group.
"Sir David is the best possible ambassador I could imagine working with," said CEO and artistic director Alastair Spalding. "He has the talent, the experience, and a real passion for our new mission."
Bell began his career as a journalist at the Financial Times and rose to the chairmanship of the paper. He was also chairman of the Millennium Bridge Trust in the 1990s and is currently chairman of Crisis, a nonprofit agency providing services for the homeless. He was knighted in 2004.
The current Sadler's Wells Theatre is the fifth by that name, the first having opened in 1683. The 20th-century incarnation, created by Lilian Baylis in 1927, was the site of the creation of English National Opera and two ballet companies, now the Royal Ballet and the Birmingham Royal Ballet. The most recent version of the theater was constructed in 1998; it hosts the Rambert Dance Company and Random Dance and presents works by artistic partners including Matthew Bourne and the Ballet Boyz.