Sir John Denis Mahon, London, England, UK (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 is also a respected scholar, he is generally credited, alongside Sacheverell Sitwell and Tancred Borenius,with bringing Italian Baroque painters to the attention of English-speaking audiences, reversing the critical aversion to their work which had prevailed from the time of John Ruskin.