The old Piazzetta of St Mark’s.
Mingling with the festive crowd are Loredano and Barbarigo, in disguise. The people incite the gondoliers by striking up a barcarole («Tace il vento, è queta l’onda»). From the Doge’s palace come two trumpeters, and on hearing their blasts the people melt away in fear. On the canal a galley sails past, bearing the ensign of St Mark. Out of the Doge’s palace comes Jacopo Foscari, followed by Lucrezia. In deep distress, he bids farewell to all (scena and aria «All’infelice veglio») while Loredano exults at the sight of his vendetta fulfilled.

The Doge’s private rooms.
Francesco Foscari, alone, ruminates over the premature death of his three sons and the sorry fate of his fourth. Barbarigo enters holding a sheet of paper declaring that the real culprit of the murder has confessed. The Doge exults, for his son’s innocence is now proven. But Lucrezia has to break the news that Jacopo, unable to bear the sorrow of having to go back into exile, died at the moment of departure (scena and aria «Più non vive!... l’innocente»). The Ten arrive and request the Doge to retire from the affairs of state and to renounce his power. At first the Doge reacts with indignation, but then he is so utterly dejected by his family woes that he relinquishes his ring (scena and final aria «Questa dunque è l’iniqua mercede»). As he goes out, with Lucrezia, he hears the bells of St Mark’s announcing the election of the new Doge. Overcome by this final affront, Francesco Foscari collapses and dies.