Space Marine Captain

A Space Marine 'Captain' (also known as Brother-Captain, or Company Captain) is a Senior rank within a Space marine Chapter. They typically commands an entire Company of his battle brothers (a customary maximum of one hundred Marines).
The ancient rank of Captain has been employed since the days of the Space Marine Legions. During the Great Crusade a Company Captain was a military rank given to the commander of a Company, a command level between Battalion and Squad, leading a force of a hundred Legionaries. Depending on the Legion, the designation would vary and could be Centurion, Prime, Wolf Lord, Blooded, Khan, etc... This position was mostly granted to Legion Centurions, elite officers of the Legions who demonstrated their worth in the fires of conflict.
With the institution of the Codex Astartes, the rank of Captain as Commander of a Company remained and is still in use in the current Era.