The Master of the Fleet is the Space Marine Captain within a Chapter compliant with the Codex Astartes who commands all of the Chapter's space assets and is deemed to have the most experience and greatest skill at planning and executing void-combats.
A Chapter Master designates one of his Captains to command the Chapter fleet, who essentially serves as the Chapter's fleet admiral, commanding its flagship and all other space assets when they deploy for major engagements.
In rare cases, a Chapter's Master of the Fleet may not be an Astartes officer but a mortal with a long history of space combat and commanding fleet engagements, such as a former or current flag officer of the Imperial Navy who has been seconded to the Chapter under ancient inter-service agreements. In Codex-compliant Chapters this office is typically held by the Captains of the 4th Company.
Notable Masters of the Fleet
- Codex: Space Marines (5th Edition) pp. 17, 54
- Warhammer 40,000: Apocalypse (6th Edition), pg. 177
- Defenders of Ultramar #1 (Comic)
- Games Workshop Online Catalogue - Space Marine Masters of the Chapter