Sir John Denis Mahon, (8 November 1910 – 24 April 2011) was a British collector and historian of Italian art.
Considered to be one of the few art collectors who was also a respected scholar, he is generally credited, alongside Sacheverell Sitwell and Tancred Borenius, with bringing Italian pre-Baroque and Baroque painters to the attention of English-speaking audiences, reversing the critical aversion to their work that had prevailed from the time of John Ruskin.
Italian photographer In 2008 his works have been bought by BEIC - Biblioteca Europea d'Informazione e Cultura (European Library for Information and Culture) of Milan. The whole amount of Paolo Monti's works consists of more than 220,000 photographic negatives, 12,000+ prints and 790 chemigrams that describe the story, society and culture of Italy from 1943 to 1982.