Army[edit]
They guard all roads in the zone, control perimeters, hunt mutants and shoot looters (Stalkers) down.
- Attitude: Hostile
- Affiliations: None
- Joinable: No
Mobile Science Lab (MSL)[edit]
A mobile lab that resembles a small heavily armored bunker with small tainted glass windows. It has its own life-support and so can work autonomously for several months.
- Attitude: Neutral
- Affiliations: Duty. If Duty is your enemy the MSL will also be hostile
- Joinable: No
Monolith[edit]
This group displays many features of a religious sect. It's members believe in an complex alien crystal, the Monolith, somewhere deep in the middle of the zone.
- Attitude: Hostile
- Affiliations: None
- Joinable: No
Duty[edit]
A paramilitary group known for it's discipline, whose Members live according to a strict code.
- Attitude: Neutral
- Affiliations: MSL
- Joinable: Yes
Bandits[edit]
Members of the Criminal underworld who came to the zone for various reasons, to make money, to sell Artifacts or to hide from the law.
- Attitude: Hostile
- Affiliations: None
- Joinable: Only in Clear Sky
Military Stalkers[edit]
Soldiers who underwent a special training in the Zone or Stalkers who voluntarily signed a contract with the army.
- Attitude: Hostile
- Affiliations: Army
- Joinable: No
Mercenaries[edit]
The most clandestine and secretive faction in the zone, some don't even believe in its existence.
- Attitude: Hostile
- Affiliations: None
- Joinable: No
Lone Stalkers[edit]
Lone stalkers who expore the zone on their own, they are not part of any faction, neither Duty, nor Freedom. Most Stalkers work this way since being part of a group takes time and more importantly loot.
- Attitude: Neutral
- Affiliations: None
- Joinable: Yes (You are one from the Beginning of the game)
Freedom[edit]
Anarchists and daredevils who declare themselves fighters for free access to the zone and consequently find themself in constant conflict Army, Military stalkers, and the Duty faction.
- Attitude: Neutral
- Affiliations: None
- Joinable: Yes