The Hanseatic League was a medieval commercial and defensive confederation of merchant guilds and market towns in Central and Northern Europe. Growing from a few North German towns in the late 12th century, the League between the 13th and 15th centuries ultimately encompassed nearly 200 settlements, across seven modern-day countries ranging from Estonia in the north and east to the Netherlands in the west and Kraków, Poland, in the south.

The League originated from various loose associations of German traders and towns formed to advance mutual commercial interests, such as protection against robbers. These arrangements gradually coalesced into the Hanseatic League, whose traders enjoyed toll privileges and protection in affiliated communities and their trade routes. Economic interdependence and kinship ties between merchant families, who held important positions in towns, led to deeper political integration and removing obstacles to trade. Hanseatic Cities gradually developed common trade regulations.

During its heydays, the Hanseatic League dominated maritime trade in the North and Baltic seas. It established trading posts in numerous towns and cities across Europe; some of these, like the Kontors in London, Bruges, Bergen and Novgorod, became extraterritorial entities that enjoyed considerable legal autonomy. Hanseatic merchants, or Hansards, operated in basic private companies and were widely renowned for their access to a variety of commodities, subsequently gaining privileges and protections abroad. The collective economic power made the League capable of imposing blockades and even waging war against kingdoms and principalities.

Even at its zenith, the Hanseatic League was never more than a loosely aligned confederation of city-states. It lacked a permanent administrative body, treasury, and standing military force. By the mid-16th century, these weak connections left the Hanseatic League vulnerable and it gradually unraveled as members became consolidated into other realms or departed, ultimately disintegrating in 1669. In the 14th century the Hanseatic League instated an irregular quasi-legislative diet (Middle Low German: dachvart or dach, German: Tagfahrt or Hansetag) that operated on deliberation and consensus.

The Hanseatic League used several types of ships that sailed over seas and on rivers. The most emblematic type was the cog. Knowing great diversity in construction, it was depicted on Hanseatic seals and coats of arms. By the end of the Middle Ages, the cog was replaced by other types like the hulk that later gave way to larger carvel types.