Master mariner

A master mariner or MM is the professional qualification required for someone to serve as the person in charge or person in command of a commercial vessel in England, and countries of the Commonwealth.

The term master mariner has been in use at least since the 13th century, reflecting the fact that in guild or livery company terms, such a person was a master craftsman in this specific profession (e.g. master Carpenter, master Blacksmith). In the United States, the term was introduced in the mid-19th century.