Factions are in-universe groups with which Guardians can align themselves. Most faction representatives are located in the Tower, selling unique weapons and armor for their factions. In addition to the main factions, there are several other sub-factions associated with certain activities and vendors.
Each faction has a reputation associated with it. Reputation is earned by performing activities, and will periodically "rank up" once a certain amount has been earned. Upon ranking up, the faction will send the player a package containing a random piece of Faction-specific gear, and for ranks 1-3 will also unlock additional items for purchase at the faction's vendor.
- The Vanguard, led by Commander Zavala, Cayde-6, and Ikora Rey, manages field campaigns against enemies on Earth and beyond.
- The Crucible, led by Lord Shaxx, manages the Guardian combat training program.
Any activity the player performs will contribute to either of these factions- Crucible matches will contribute to Crucible, while Story Missions, Strikes, and Patrol will contribute to Vanguard. Bounties from Berg 99-40 or Xander 99-40 will also contribute to these factions.
- Future War Cult, led by Lakshmi-2, believes that war and conflict are the only worthy cause that exists and that humanity must always be prepared and willing to fight.
- Dead Orbit, led by Arach Jalaal, believes that humanity's highest priority should be to leave Earth behind and spread out through the cosmos.
- New Monarchy, led by Executor Hideo, believes that the City's government should be replaced with a single benevolent dictator.
A player must pledge to one of these factions in order to earn reputation with them; doing so will cause any activity that earns Vanguard or Crucible rep to also earn faction rep. A player may only be pledged to one faction at a time and may only pledge to a new faction once per week.
- The Cryptarch has his own reputation, which is earned by decrypting Engrams. Ranking up will award a package containing additional engrams.
- Queen's Wrath is managed by Petra Venj, and rep may be earned by participating in House of Wolves quests and completing her bounties. Her reward packages contain Reef-themed Year 1 weapons.
- Iron Banner has its own faction, led by Lord Saladin, whose rep is earned by completing matches and bounties in the Iron Banner playlist. It has a maximum rank of 5, and will deliver reward packages upon reaching ranks 3 and 5 only.
- Crota's Bane is the faction associated with Eris Morn. Its rep may be earned by completing the The Dark Below quests and participating in Court of Oryx events. Her reward packages contain Court runes and Moldering Shards.
- Sparrow Racing League has a faction managed by Amanda Holliday, whose reputation may be earned by completing races and bounties. Reward packages contain racing sparrows and horns.
- House of Judgment is a faction managed by Variks, and is earned by completing matches in the Prison of Elders. Upon reaching rank 3, the player will be awarded a package containing resources and consumables at each Weekly Reset.
- Banshee-44 manages the Gunsmith faction. Rep is earned by completing the tasks assigned to test weapons.