Ultramarines
The Ultramarines are one of the First-Founding Legions of the Space Marines. Their primarch is Roboute Guilliman, whose leadership abilities (not to mention the Codex Astartes) were instrumental in humanity's survival during the Horus Heresy. Given that their primarch wrote the text that defines a Space Marine chapter in the 41st millennium, the Ultramarines follow this Codex strictly; in fact, the only deviation whatsoever are the relatively recent Tyrannic War Veterans, composed entirely of veterans of the infamous Battle for Macragge.
Homeworld
The Ultramarines are unique in that, unlike their fellow chapters, they control several systems, rather than a single planet. Collectively, these systems are known as Ultramar, with Macragge as its capital. Macragge is a cold and rocky world, though certainly capable of sustaining life, and is home to the Fortress of Hera, where the Ultramarines are stationed.
Organization
Like all Codex chapters, the Ultramarines are divided into ten companies of 100 Marines each. The First Company is composed entirely of veterans, and has only recently been brought to full strength after being killed to a man defending the polar regions of their homeworld during the Battle for Macragge. Companies two through five are the Battle Companies, containing a mix of Tactical, Assault, and Heavy Support marines. Companies six through nine are the Reserve Companies, and the Tenth Company are the Scouts.
(Note: this article is currently incomplete. Feel free to add relevant information)
