Thomas W. Gaehtgens (born June 24, 1940 in Leipzig) is a German art historian with special interest in French and German art and art history from the 18th to the 20th century. He was the founding director of the Deutsches Forum für Kunstgeschichte in Paris (Centre Allemand d'Histoire de l'Art de Paris; German Center for the History of Art, Paris) and is currently director of the Getty Research Institute in Los Angeles, California.
In 1966, Gaehtgens completed his Ph.D. dissertation on the French Renaissance sculptor, Germain Pilon, at the University of Bonn. In 1972 he published his Habilitationsschrift about Joseph-Marie Vien at the University of Göttingen. For some years he worked as an adjunct professor at the Art History Seminar of this university. From 1979 to 1980, he spent some research time at the Institute for Advanced Study in Princeton, New Jersey. From 1980 until his retirement in 2006 he was Professor of Art History at the Free University of Berlin.
Soon after his appointment to Berlin's University, Gaehtgens began turning his attention to pre-twentieth-century American art, which was not a primary field for art historians at German universities at that time. In 1985–86 he was a visiting scholar with the Getty Center for the History of Art and the Humanities. In 1988, this led to a major exhibition of American 18th- and 19th-century painting in Germany. In 1992, Gaehtgens took over the organization of the Twenty-Eighth International Congress of the History of Art in Berlin. From 1992 to 1996, Gaehtgens was president of the Comité International d'Histoire de l'Art (CIHA), which is supported by the Association of Art Historians. In 1997, he founded, with German, French, and Swiss colleagues, the Deutsches Forum für Kunstgeschichte in Paris (Centre Allemand d'Histoire de l'Art de Paris), which organizes conferences, symposia, and workshops, undertakes research projects, and has published many books on art. From 1998 to 1999 he was Chaire européenne at the Collège de France. In 2004, he received an honorary doctorate at the Courtauld Institute of Art, London.