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The Treaty or Peace of Venice, 1177, was a peace treaty between the papacy and its allies, the north Italian city-states of the Lombard League, and Frederick I, Holy Roman Emperor. The Norman Kingdom of Sicily also took part in negotiations and the treaty thereby determined the political course of all Italy for the next several years.
The treaty followed on the heels of the Battle of Legnano of 29 May 1176, a defeat for Frederick Barbarossa. Frederick quickly thereafter sent envoys to Pope Alexander III at Anagni, asking for an end to the schism between him and Frederick's antipope, Callixtus III. After a preliminary agreement was reached, a conference was scheduled for July 1177. Frederick spent some time in the interim interfering in Venetian rivalries in hopes of securing a pro-Imperial group in power at the time of the confrontation.
On 24 July, the pope from the Basilica di San Marco sent a delegation of cardinals to the emperor in the Lido, at the mouth of the Venetian Lagoon. The emperor formally acknowledged Alexander as pope and abandoned his own antipope; the cardinals formally lifted the excommunication that had hitherto been placed upon him. Sebastian Ziani, the doge of Venice, and Ulrich II von Treven, the patriarch of Aquileia, then escorted the emperor into Venice itself. The delegates of the king of Sicily were Romuald, Archbishop of Salerno, a chronicler who left an eyewitness account of the scene, and Count Roger of Andria.
In the treaty that was concluded, the emperor recognised the temporal rights of the popes over the city of Rome, but the city did not surrender to the pope and forced him to leave in 1179. A fifteen-year peace was concluded between Frederick and William II of Sicily, paving the way for Sicily's golden years of peace and prosperity. Likewise, a six-year truce was concluded with the Lombard League, but negotiations were to continue, and the emperor finally recognised the independence of the Lombard cities in the Peace of Constance of 1183.