Andrea Tron (1712 - 1785) served twice as Venetian ambassador, to Paris and to Vienna. He was elected a Procurator of S. Marco in 1773 and became a notable figure in Venetian politics. He narrowly missed being elected doge. Here he is depicted as a 'Cavaliere della stola d'oro' - he wears the insignia across his left shoulder. This honour was usually bestowed by the senate when an ambassador returned to Venice, and Tron may have received it after returning from Paris in 1748 (see also Tintoretto's 'Portrait of Vincenzo Morosini').
The identity of the sitter is confirmed by the Tron coat of arms on the surmount of the original frame (the only part of it which survives), and by an engraving by Felice Zuliani after the picture giving the subject's name. The engraving was issued in 1773, so this painting must pre-date that year.