Full list of all 85 XCOM: Enemy Unknown achievements. It takes around 200 hours to unlock all of the achievements in the base game on Windows.
The base game contains 50 achievements, and there are 2 DLC packs containing 35 achievements.
Win the game from each of the 5 starting locations.
Shoot down 40 UFOs.
Beat the game in Ironman mode on Classic or Impossible Difficulty.
Beat the game on Impossible difficulty.
Beat the game on Classic difficulty.
Complete a Very Hard abduction mission in five turns or less on Classic or Impossible difficulty.
Clear a UFO crash site with one soldier on Classic or Impossible difficulty.
Kill 500 aliens.
Beat the game on any difficulty.
Have a soldier survive every mission in a full game.
Make contact with the Ethereal hive mind.
In a single game, complete every Foundry project.
Mind Control an Ethereal. Single player only.
In a single game, complete every Research Project.
In a single game, shoot down one of each alien craft.
Build the Gollop Chamber.
Kill 50 aliens with explosive weapons.
Kill an alien while flying. Single player only.
In a single game, complete every Autopsy.
Successfully assault an Overseer UFO.
Build a Firestorm.
Staff the Research Labs with 80 scientists.
Find a soldier with the Gift.
Build the Hyperwave Relay.
Kill 150 aliens.
Acquire 1000 credits in one month.
Recover the Hyperwave Beacon.
Staff the Engineering Department with 80 engineers.
Fulfill a Council request.
Build a suit of powered armor.
Advance one of your soldiers to Colonel rank.
Build a S.H.I.V.
Earn the "Excellent" rating in every performance category on a terror mission.
Uncover the alien base's location.
Stun an Outsider.
Get satellite coverage over every country on one continent.
Build a Workshop.
Win a mission with an all-female squad. Single player only.
Capture a live alien.
Gain access to the lowest level in your base.
Build a Laboratory.
Shoot down a UFO.
Launch a Satellite.
Complete a Research Project.
Build a base facility.
Build an item.
Complete a mission without losing a soldier.
Complete the tutorial mission.
Win a multiplayer match.
Play a multiplayer match against someone with this achievement.
Take your new ally into the final challenge.
Complete Gangplank.
Complete Confounding Light with more than 3 turns left on the timer.
Complete Confounding Light.
Complete Friends in Low Places.
Beat the game without buying a Squad Size upgrade (Classic+ difficulty)
Designate a highly decorated soldier as the Volunteer
Deal with the newest global threat
Kill an unseen enemy detected by a specially modified soldier in single player
Deploy three tactical subsystems on a single soldier in single player
Field a squad consisting entirely of augmented soldiers and SHIVs (min. 4) and win the mission
Kill a Muton Berserker in melee combat in single player
Make certain of the new threat's location
Field a squad with 4 augmented soldiers, each with a different base ability and win the mission
Use Collateral Damage to blow up a car in single player
Kill an enemy as it is psionically attacking you in single player
Field a squad where all members have at least two modifications (min. 4) and win the mission
Proc Combat Rush on the entire squad (min. 4)
Kill an elite enemy Medic with explosive damage in single player
Kill an elite enemy Sniper with one of your own snipers in single player
Complete Furies
Get a Soldier to have 5 modifications in single player
Complete Deluge
Eliminate an enemy's shield and kill it on the same turn in single player
Eliminate all alien waves
Get at least 4 kills with XCOM Base Security personnel
Beat a new special mission without losing any assets
Have your special-duty soldier kill three enemies in the same mission
Cause an enemy to suicide
Field a fully enhanced squad and win the mission
Jump two stories in one move in single player
Eradicate the infestation
Augment a soldier in single player
Modify a soldier in single player
Stop a squad member from suffocating in single player