There are 79 achievements with a total of 1750 gamerscore.
| Unlockable: | How to unlock: |
| Alas, Poor Yorick (25 gs) | On a Legendary map, get 3 Oddball melee kills during any ranked or social match. |
| Defend This (50 gs) | On a Legendary map, get a flag melee kill during any ranked or social match. |
| Cleansing (30 gs) | Finish the fifth mission of the Campaign on Normal, Heroic, or Legendary. |
| Spartan Officer (25 gs) | Advance to the Spartan Officer ranks (Online). |
| Mongoose Mowdown (5 gs) | Splatter an enemy with the mongoose in a ranked free for all playlist (Online). |
| Campaign Complete: Heroic (125 gs) | Finish the Campaign on Heroic (unlocks achievement for Normal, if not earned). |
| Came… From… Behind (50 gs) | On a Legendary map, get 3 assassinations during any ranked or social match. |
| Road Rage (25 gs) | On a Legendary map, get 5 Warthog chaingun kills during any ranked or social match. |
| Holdout (20 gs) | Finish the second mission of the Campaign on Normal, Heroic, or Legendary. |
| The Road (20 gs) | Finish the third mission of the Campaign on Normal, Heroic, or Legendary. |
| Graduate (10 gs) | Earn 5 EXP or finish 10 games to complete the requirements for basic training (Online). |
| Lee R Wilson Memorial (5 gs) | Score 5 grenade sticks in any ranked free for all playlist (Online). |
| Landfall (20 gs) | Finish the first mission of the Campaign on Normal, Heroic, or Legendary. |
| Iron (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Flag Dropped (25 gs) | On a Legendary map, get 2 flag carrier kills during any ranked or social match. |
| Hammer Time (25 gs) | On Assembly, get 5 Hammer kills during any ranked or social match. |
| Up Close and Personal (5 gs) | Kill 5 enemies by melee or assassination in a ranked free for all playlist (Online). |
| Tough Luck (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Refuge (30 gs) | Finish the sixth mission of the Campaign on Normal, Heroic, or Legendary. |
| Assault (30 gs) | Finish the fourth mission of the Campaign on Normal, Heroic, or Legendary. |
| UNSC Spartan (15 gs) | Earn your Sergeant rating to be recognized as a true Spartan (Online). |
| Ghost Patrol (25 gs) | On Longshore, get 3 kills with a Ghost during any ranked or social match. |
| Look Both Ways (50 gs) | On a Legendary map, get a Splatter Spree during any ranked or social match. |
| Tilt (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Campaign Complete: Normal (125 gs) | Finish the Campaign on Normal. |
| Blades of Fury (25 gs) | On Heretic, get a Sword Spree during any ranked or social match. |
| Pull (25 gs) | On Citadel, get a Shotgun Spree during any ranked or social match. |
| Return (50 gs) | Finish the final mission of the Campaign on Normal, Heroic, or Legendary. |
| Catch (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| We’re in for some Chop (5 gs) | Destroy an enemy vehicle with equipment in a ranked playlist or in campaign. |
| Killing Frenzy (5 gs) | Kill 10 enemies without dying in any ranked free for all playlist (Online). |
| Last Stand (40 gs) | Finish the seventh mission of the Campaign on Normal, Heroic, or Legendary. |
| Two for One (5 gs) | Score a Double Kill with a single spartan laser shot in a ranked free for all playlist (Online). |
| MVP (5 gs) | Earn the MVP in any ranked playlist (Online). |
| … Get the Horns (25 gs) | On a Mythic map, get a Bulltrue medal during any ranked or social match. |
| Post Mortem (25 gs) | On Orbital, get 2 Death From the Grave medals during any ranked or social match. |
| Black Eye (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Used Car Salesman (5 gs) | Destroy a vehicle that has three enemies in it in a ranked playlist or in campaign. |
| Campaign Complete: Legendary (125 gs) | Finish the Campaign on Legendary (unlocks achievements for Normal and Heroic, if not earned). |
| Too Close to the Sun (5 gs) | Destroy an enemy banshee with the spartan laser or missile pod in a ranked playlist or in campaign. |
| Guerilla (10 gs) | Score over 15,000 points in the Campaign meta-game on the first mission. |
| Awww, Too Bad (25 gs) | On a Mythic map, get a Killjoy medal during any ranked or social match. |
| Have Fun Respawning (25 gs) | On a Mythic map, get an Extermination during any ranked or social match. |
| Maybe Next Time Buddy (5 gs) | Board the same vehicle within 10 seconds after being boarded in any free for all playlist (Online). |
| The Key (40 gs) | Finish the eighth mission of the Campaign on Normal, Heroic, or Legendary. |
| Steppin' Razor (5 gs) | Score a Triple Kill with the sword in a ranked free for all playlist (Online). |
| Demon (10 gs) | Score over 15,000 points in the Campaign meta-game on the second mission. |
| Killtacular (25 gs) | On a Mythic map, get a Killtacular during any ranked or social match. |
| Save This Film (25 gs) | On a Mythic map, get a Perfection medal during any ranked or social match. |
| Askar (10 gs) | Score over 15,000 points in the Campaign meta-game on the fourth mission. |
| Thunderstorm (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Fear the Pink Mist (5 gs) | Kill 5 enemies with the needler in a ranked free for all playlist or in campaign. |
| Headshot Honcho (5 gs) | Kill 10 enemies with headshots in a ranked free for all playlist or in campaign. |
| Triple Kill (5 gs) | Kill 3 enemies within 4 seconds of one another in a ranked free for all playlist (Online). |
| Tank Dropper (25 gs) | On any Mythic map, get a kill on another player while in monitor mode. |
| Assembly Skull (25 gs) | On Assembly, find the hidden skull. |
| Cavalier (10 gs) | Score over 15,000 points in the Campaign meta-game on the third mission. |
| Famine (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Sandbox Skull (25 gs) | On Sandbox, find the hidden skull. |
| Orbital Skull (25 gs) | On Orbital, find the hidden skull. |
| Fog (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Ranger (10 gs) | Score over 50,000 points in the Campaign meta-game on the sixth mission. |
| Longshore Skull (25 gs) | On Longshore, find the hidden skull. |
| Heretic Skull (25 gs) | On Heretic, find the hidden skull. |
| Vanguard (10 gs) | Score over 50,000 points in the Campaign meta-game on the seventh mission. |
| Overkill (5 gs) | Kill 4 enemies within 4 seconds of one another in a ranked free for all playlist (Online). |
| Mythic (10 gs) | Find and claim this skull when playing on Normal, Heroic or Legendary difficulty. |
| Zombie Repeller (25 gs) | On a Mythic map, kill 2 Zombies during any ranked or social match. |
| Citadel Skull (25 gs) | On Citadel, find the hidden skull. |
| Reclaimer (10 gs) | Score over 15,000 points in the Campaign meta-game on the final mission. |
| Delicious Brains (25 gs) | On a Mythic map, infect 2 humans during any ranked or social match. |
| Double Double (25 gs) | On a Legendary map, get two Double Kills during any ranked or social match. |
| Orpheus (10 gs) | Score over 15,000 points in the Campaign meta-game on the eighth mission. |
| Marathon Man (40 gs) | Locate and access all Terminals in the Campaign. |
| Exterminator (10 gs) | Score over 15,000 points in the Campaign meta-game on the fifth mission. |
| Vidmaster Challenge: Brainpan (25 gs) | Find all the hidden skulls on the Mythic maps. |
| Vidmaster Challenge: Lightswitch (0 gs) | Get to the rank of Lieutenant in any playlist in the new EXP progression system. |
| Vidmaster Challenge: 7 on 7 (0 gs) | Enter into any ranked or social playlist with 7 EXP on the 7th of the month. |
| Vidmaster Challenge: Annual (0 gs) | After 9/25/08, complete Halo on 4-player Legendary LIVE co-op, with Iron, and everyone in Ghosts. |
