In the medieval feudal societies, finance had traditionally depended on the ownership of land as the foremost source of wealth and income. Over time, however, the excessive demand for resources by rivalrous European rulers, together with the continuous expansion of trade routes and international commercial relationships, offered opportunities for financial innovation, while the growing volume of transactions also led to increased specialisation. Finance, thus, gradually evolved from auxiliary services into a sophisticated business. This chapter tracks some major developments of the era, ranging from novel instruments to the management of sovereign debt, commercial credit and the origins of modern corporations, and addresses the early theoretical contentions that were induced by the expansion of financial innovation.