The Lombard League was an alliance formed on December 1, 1167 between 26 (later 30) cities of North Italy, including Cremona, Mantua, Bergamo, Brescia, Milan, Bologna, Padua, Treviso, Vicenza, Verona, Lodi, and Parma. The League was formed to counter the Holy Roman Empire's Frederick I, who was attempting to assert Imperial influence over Italy. Frederick claimed direct Imperial control over Italy at the Diet of Roncaglia (1158), and invaded Italy in 1158 and 1166. The League had the support of Pope Alexander III, who also wished to see Imperial power in Italy decline. At the battle of Legnano on May 29, 1176, Frederick I was defeated. After several more defeats, the Emperor agreed to a six-year truce from 1177 to 1183, until the Treaty of Constance, where the Italian city-states agreed to remain loyal to the Empire but retained local jurisdiction over their territories.

The Lombard League was renewed in 1198 and 1208. In 1226, the League regained its former prestige by countering the efforts of Frederick II to gain greater power in Italy. These efforts included the taking of Vicenza and the Battle of Cortenuova which established the reputation of the Emperor as a skillful strategist. He misjudged his strength, rejecting all Milanese peace overtures and insisting on unconditional surrender. It was a moment of grave historic importance when Frederick's hatred coloured his judgment and blocked all possibilities of a peaceful settlement. Milan and five other cities held out, and in October 1238 he had to unsuccessfully raise the siege of Brescia. Once again receiving papal support, the Lombard League effectively countered Frederick's efforts, and the League was dissolved in 1250 once Frederick died.

The Lombard League was also a 1984-1991 precursor to the Italian political party known since 1991 as the Lega Nord ("Northern League").