A master craftsman or master tradesman (sometimes called only master or grandmaster) was a member of a guild. In the European guild system, only masters and journeymen were allowed to be members of the guild.
An aspiring master would have to pass through the career chain from apprentice to journeyman before he could be elected to become a master craftsman. He would then have to produce a sum of money and a masterpiece before he could actually join the guild. If the masterpiece was not accepted by the masters, he was not allowed to join the guild, possibly remaining a journeyman for the rest of his life.
Originally, holders of the academic degree of "Master of Arts" were also considered, in the Medieval universities, as master craftsmen in their own academic field.