Mark could refer to:
- Mark (Day 1) - Ted Cofell's usual limo driver during Season 1.
- Mark (Day 2) - a contact of Ryan Chappelle during Season 2.
- Mark (Day 6) - A CTU field agent seen during Season 6.
- Mark Bishop - a mole working for the Russian government.
- Mark Bledsoe - chief contractor recommended by Charles Logan to President Allison Taylor during Season 8.
- Mark DeSalvo - Head of the level 3 detention facility in Saugus during Season 1.
- Mark Hauser - Made a deal with Dmitri Gredenko during Season 6.
- Mark Kaner - was a high-level advisor on the staff of Senator, then President, John Keeler.
- Mark Wexler - With Doug Masters, he guarded James Heller for part of Season 5.
- Mark Boudreau - President James Heller's Chief of Staff for Season 9.