From the Wikipedia page 
The Hague Club is formed by the Chief Executives of ca 30 major private Foundations in Europe. It meets once a year to discuss informally the role of philanthropy and management of Foundations. Founded in 1971, it claims to be independent of governments and to have no political aims.
Foundations with directors currently members of the Club include the Finnish Cultural Foundation, Nobel Foundation, Rockefeller Brothers Fund and the Oranje Foundation.
The Saint-Simon Foundation was a member of the Hague Club until shortly before it dissolved in 1999.
The website is .