Guild, economic and social association of merchants or craftspeople in the same trade or craft to protect the interests of its members. Guilds flourished in Europe in the Middle Ages. Merchant guilds were often very powerful, controlling trade in a geographic area; the Hanseatic League controlled trade in much of northern Europe. The craft guilds (as of goldsmiths, weavers, or shoemakers) regulated wages, quality of production, and working conditions for apprentices. Wealthy guilds built extensive headquarters for themselves, some of which still stand. The guild system declined from the 16th century because of changing trade and work conditions.