The Ultramarines hold a unique position, as the Chapter is in control of the entire Ultramar sub-sector, nine star systems and eleven worlds, instead of the single home planet common to most. They also possess an exceptionally large space fleet. These resources, as well as their immense accomplishments and originating the Codex Astartes, give the Ultramarines Chapter considerable influence, even if their actual Space Marine infantryman count is limited to 1,000 Astartes by the Codex.
- Roboutte Guilleman - Primarch, original genetic template of the XIII Legion's Astartes and the author of Codex Astartes. Mortally wounded by Fulgrim and in stasis on Macragge as of M41.
- Marneus Calgar - Chapter Master as of late M41.
- Captain Titus - Captain, 2nd Company (in the Space Marine video game)
- Sidonus - Veteran Sergeant, 2nd Company Command Squad
- Leandros - Veteran, 2nd Company Command Squad
- Cato Sicarius - Captain, 2nd Company (in official Warhammer 40,000 lore)
- Varro Tigurius - Chief Librarian of the Ultramarines, the most powerful Imperial Psyker in the galaxy, except for the Emperor
- Captain Severus - Captain, 2nd Company (in the movie Ultramarines)