Charles Ephrussi was a wealthy amateur art historian, art critic and collector.
Ephrussi was founder and editor of what became the most prestigious and influential art historical journal in France, the Gazette des Beaux-Arts. He also published widely on art; his works include Albert Dürer et ses dessins (1882) and Grands peintres français et étrangers; ouvrage d'art, publié avec le concours artistique des maîtres; texte par les principaux critiques d'art (1884-6).
Marcel Proust is said to have based the character of Swann on Charles Haas and Ephrussi in his novel A la recherche du temps perdu (1913-1927).
'Charles Ephrussi', Wikipedia.