During the last half of the thirteenth and first half of the fourteenth centuries, there emerged a number of very large Italian merchant banking companies. Three of them, the Bardi, Peruzzi, and Acciaiuoli companies of Florence, attained exceptional size, diversity, and geographical reach, but all collapsed in the 1340s. The two largest, the Bardi and Peruzzi, came to grief, according to the chronicler Giovanni Villani, because they advanced loans foolishly and excessively to King Edward III of England to help him finance the opening phases of the Hundred Years' War. Villani claimed that the English king owed the Peruzzi Company the colossal sum of 600,000 Florentine florins when it went bankrupt in 1343, and the Bardi an even larger total of 900,000 florins when it failed in 1346.

Most students and general readers have become aware of the existence of these great organizations from popular political or social histories of the period in which the Bardi and Peruzzi are briefly introduced and promptly dismissed. In such accounts, the firms are characterized as banking houses that naively and greedily overreached themselves in lending huge sums to the king in the vain pursuit of profit. But many other historians have written thoroughly researched works in various languages about particular aspects of the companies' activities, including their role in the history of medieval Florence, or about the operations of individual branches in southern Italy, Sicily, England, France, and the papal courts.