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"Hey, you're that new guy headed for the old comm center, right? You'd better hustle up, pal."
― Mark Ryan, upon meeting the Marine  [src]

Mark B. Ryan (Identification Number: 9368-41) is a minor character in Doom 3. A Mars-Sec security officer assigned to Mars City Underground, he guarded the airlocks connecting the Underground and the abandoned communications facility.

When the player meets Ryan, he momentarily receives an email from T. Brooks in his PDA about their arrival. Ryan directs the player towards the communications facility, explaining to them that they must quickly traverse through the Martian surface outside before potentially suffocating.

During the demon invasion, when the player enters the airlock to the Underground, it malfunctions and only opens enough for the player to see a dead Ryan getting dragged away by a Zombie. The airlock then opens enough for the player to exit the airlock and kill the Zombie.

PDA contents[]


Got a new guy on the way (11-15-2145)[]

Hey Mark,
We had a new marine just come through the security checkpoint. He's gonna check out the old comm building for that missing scientist. Can you make sure he doesn't get lost... last thing we need is another missing person.

Thanks Bro


  • It's possible to shoot Mark and pick up his PDA to read Brook's e-mail about the player's arrival. Although he doesn't appear in the Xbox port, his PDA can still be found.
  • Mark Ryan is the last living security guard the player encounters in the game. Afterwards, all security guards encountered post-invasion are Z-Secs.