Grandmarines

| name                 = Grandmarines | shoulder artwork     = | shoulder caption     = | colour scheme        = | colour scheme caption = | founding             = 8th | primarch             = Roboute Guilliman | chapter master       = Crycer Duron | homeworld            = Grower | fortress monastery   = Tower of Duron | allies               = Deathwatch, Grey Knights, Ultramarines | number of marines    = 900 | specialty            = Anti-Xenos, Anti-Daemon | battle cry           = | colours              = Chaos Black, Blood Red & Gold | successor chapters   = N/A

"Through multiple campaigns and hardships, against Xenos, Mutants and other enemies of the Imperium, I have learned to only trust myself, and the Emperor."

—Crycer Duron, Chapter Master of the Grandmarines.

The Grandmarines are and 8th Founding successor chapter of the Ultramarines, they police the Grower sector, in the Segmentum Ultima. Their homeworld is the primary planet in the sector, the Fortress World of Grower, which when they found it, was swarmed in Daemons, Xenos and other enemies of the Imperium, a great purge was held, cleansing the world of the filth that slept there.

After purging the world, the Grandmarines purged the other planets in the sector, finding multiple Chaos Sorcerors and Chaos Champions hiding in the underbellys of the worlds.

The Grandmarines Chapter Master, Crycer Duron, is a hot headed, bad tempered veteran of multiple campaigns, he wields, among other things, a Daemonhammer, and a strange weapon only known as 'The Daemonsabre'.