| Description | Name |
| Protagonist of Half-Life and sequels | |
| Male sidekick in Half-Life 2 and sequels | |
| Female sidekick in Half-Life 2 and sequels | |
| Mysterious antagonist of the Half-Life universe | |
| Main antagonist of Half-Life 2 | |
| Leader of the Resistance in Half-Life 2 and sequels | |
| Prominent scientist of the Resistance in Half-Life 2 and sequels | |
| Prominent scientist of the Resistance, introduced in Episode Two | |
| Robotic animal sidekick | |
| | Description | Name |
| Female scientist of the Resistance | |
| Mentally insane resident of Ravenholm | |
| 'Protagonist' of Half-Life: Opposing Force | |
| Protagonist of Half-Life: Decay | |
| Protagonist of Half-Life: Decay | |
| Protagonist of Portal | |
| Main antagonist of Portal | |
| Prominent scientist in Half-Life: Decay | |
| Prominent scientist in Half-Life: Decay | |
| Pet headcrab | |
| Member of the resistance | |
|