The player (or player character) is the entity or thing in the game controlled by a person playing the game (the player as an individual, or the game user), either alone, or as one of several in multiplayer mode. The entity has various attributes, such as a position on the map, health, and items possessed which vary according to the user's actions within the game levels.
Since the game is played from a first person perspective, a player does not see his or her sprite on the main portion of the screen, except for a hand or two when certain weapons are selected or used.
In Doom and Doom II, the player stands for an unnamed battle-hardened marine sent to Mars for a violent response against an irresponsible commander (see Doom's protagonist), while in other Doom engine based games it is a particular character fitting the corresponding background story.
In the Doom games, the player's face is shown on the status bar, where it reflects the character's health (becoming progressively bloodier as the player's health falls) and reacts to events such as being attacked, stepping on a damaging floor, or finding a weapon or power-up.
The player moves in response to the keyboard, mouse or joystick at either walking speed or running speed. The forward/backward speeds are somewhat higher than the sideways speed; these movements can be combined advantageously via straferunning. The maximum turning speed with the mouse may be adjusted by the user, although it may trigger a bug in the menu system if set very high.
In a multiplayer game, the other players appear as marines in differently colored uniforms and armor. In the Doom games the colors are green, indigo (gray), brown, and red, although various source ports permit more choices of color, and sometimes more than four players in a game. The sprites for a player are rendered in a green suit; to draw another player, the rendering engine remaps the shades of green to shades of the corresponding color.
A player spawns with 100% health, a pistol, and 50 bullets. The fists may also be used as a weapon. In Hexen, on the other hand, the player's attributes depend on the chosen character class. When respawning after being killed, all acquired items (such as armor, non-default weapons, ammo, power-ups, and keys) are lost. In deathmatch mode, one exception is made to this, as players always spawn with all the keys.
In order to be playable in single player mode, a level must have a player 1 start thing, and player starts 2 through 4, typically located close by, will enable cooperative play. Deathmatch start positions are usually located far from each other, and one is chosen at random each time a player spawns. The absence of player starts will cause a single player or cooperative game to crash, and a deathmatch game to exit with an error message.
 Doom player data
- Maximum value specified, speed varies between zero and the maximum. The player's speed varies from that of normal monsters. The base value is obtained from the control input which is then applied to the player object in the game simulation. The actual speed is around 33% of the base speed.
- Used if the player is brought below -50% health by the killing blow, but without being gibbed.
- Wall run speeds vary based on the angle against the wall.
- In earlier versions of Doom, the player would originally use a rifle as the initial weapon. The player sprites (and subsequently the zombieman) still use such a weapon in final releases.
- Unlike the zombieman and shotgun guy, the player's weapon can still be seen along with his corpse during the death animation.
- By mistake, the boots of the player during the gibbing death animation are dried in blood, similar to the zombies.
- While all corpses of marines present in regular levels are green, it appears that the marine uniforms come in a variety of colors, as seen with other players in multiplayer or former humans.
- The player view is set at a height of 41 units, which is somewhat around the height of the chest instead of the eyes. This becomes noticeable when getting closer to the sprite of another player.
 Player characters
- The marine
- the mercenary