Merchant

A merchant is a person who trades in products and commodities to amass wealth. Regardless of their origins, merchants can amass enough wealth allowing them to gain power and influence.

Cities such as Pentos, Qarth, and Astapor are ruled by elites of wealthy merchants.

In the books
In the A Song of Ice and Fire merchants are a prominent class in Essos, while in Westeros they are still looked down by the aristocracy, whose power derives from land and military power while their prestige stems from the antiquity of their bloodlines.