Bosun

Boatswain

The boatswain aboard a modern merchant ship stands cargo watch as freight is lowered into an open hatch.
General
Other names	Bosun Petty Officer Chief rate
Department	Deck department
Licensed	No
Requirements	Typically, able seaman certificate
Watchstanding
Watch (at sea)	On smaller vessels (varies)
Watch (in port)	On smaller vessels (varies)

A boatswain (/ˈboʊsən/, formerly and dialectally also /ˈboʊtsweɪn/), bo's'n, bos'n, or bosun, also known as a Petty Officer or a qualified member of the deck department, is the seniormost rate of the deck department and is responsible for the components of a ship's hull. The boatswain supervises the other members of the ship's deck department, and typically is not a watchstander, except on vessels with small crews. Additional duties vary depending upon ship, crew, and circumstance.

The word boatswain has been in the English language since approximately 1450. It is derived from late Old English batswegen, from bat (boat) concatenated with Old Norse sveinn (), meaning a young man, apprentice, a follower, retainer or servant. Directly translated to modern Norwegian it would be båtsvenn, while the actual crew title in Norwegian is båtsmann ("boats-man"). The phonetic spelling bosun has been observed since 1868. This latter spelling was used in Shakespeare's The Tempest written in 1611, and as Bos'n in later editions.

The rank of boatswain was until recently the oldest rank in the Royal Navy, and its origins can be traced back to the year 1040. In that year, when five English ports began furnishing warships to King Edward the Confessor in exchange for certain privileges, they also furnished crews whose officers were the master, boatswain, carpenter and cook. Later these officers were "warranted" by the British Admiralty. They maintained and sailed the ships and were the standing officers of the navy.