This is a list of characters with articles or unnamed characters entries who were antagonists during Day 5.
Day 5's antagonists can be divided into two categories; the Dawn Brigade Russian separatists that acquired highly lethal Sentox gas, and the members of the Sentox nerve gas conspiracy whose plot to trick the separatists went awry.
Dawn Brigade separatists
First cell
Anton Beresch initiates the takeover of the Ontario Airport.
Anton Beresch: leader of the Dawn Brigade's plot at the Ontario Airport; martyred himself when nearing capture
- Chevensky: terrorist and liaison between Beresch and Ivan Erwich at the Ontario Airport
- Gunman #1: Beresch's lieutenant at the Ontario Airport
- Ibrim: one of Beresch's terrorists at the Ontario Airport
- Vlad: one of Beresch's terrorists
- Ivan: one of Beresch's terrorists (not Ivan Erwich)
- Ishmael: one of Beresch's terrorists
- Achmed: one of Beresch's terrorists
Second cell
Ivan Erwich, the man who activated the canisters and discovered the conspiracy.
Ivan Erwich: leader of this sub-cell; was secretly a plant among Beresch's hostages who was responsible for transferring out the gas canisters from the airport after Beresch's attack was used as a cover up; stabbed by Bierko
- Andrei: Erwich's right hand man; devised a makeshift way to disperse the gas from the canisters; later worked directly for Bierko
- Komar: terrorist at the Sunrise Hills Shopping Mall; neck broken by Jack Bauer
- Polakov: terrorist at the Sunrise Hills Shopping Mall; killed himself to evade capture by CTU
- Jacob Rossler: software programmer, was hired to help the terrorists activate the nerve gas canisters
- Sergei Voronov: mutual associate of Rossler and Erwich who put them into contact
- (Rossler security guard #1: one of two security guards outside Rossler's penthouse, shot at Jack and Curtis, but was killed by Jack)
- (Rossler security guard #2: the main desk security guard at Rossler's apartment building)
Primary cell
The leader of the Dawn Brigade, Vladimir Bierko.
Vladimir Bierko: leader and financier of the Dawn Brigade, planned the later nerve gas attacks, the attack on the Suvarov motorcade and the Natalia takeover; neck snapped in self-defense by Jack Bauer
- Viktor Grigorin: terrorist, tried to gas a hospital to distract CTU; shot by Curtis Manning
- Ostroff: Bierko's sub-commander; infiltrated CTU and released a canister of nerve gas there, shot by Jack moments afterwards
- Ostroff's lieutenant: Ostroff's right hand man who led the attack on the Suvarov's motorcade; killed by Aaron Pierce
- Eric: a terrorist who was part of the team that attacked the motorcade; killed by Aaron Pierce
- Mikhail: Bierko's right hand man after Ostroff's death.
- Crewcut separatist: originally worked with Erwich but joined the primary cell after Bierko killed Erwich
- Bierko's technician: technician and final lieutenant after Mikhail's death
- Bierko's terrorist: one of Bierko's last remaining subordinates
Bierko's external supporters
- Collette Stenger: information broker who sold schematics of the Wilshire Gas Company to Bierko and framed Audrey Raines; incarcerated
- Joseph Malina: arms dealer with connections to Henderson; sold information to help Bierko board the Natalia
- Jenny McGill and Dwayne Thompkins: planned to sell Lynn McGill's keycard to Ostroff for money, but Ostroff murdered them instead to reprogram the key card to commit the Sentox attack
American Sentox nerve gas conspiracy participants
Christopher Henderson & Omicron mercenaries
Christopher Henderson, an important manager of the ground operations of the conspiracy.
Christopher Henderson: ex-mentor of Jack and former CTU director, orchestrated the murders of David Palmer, Tony Almeida, and Michelle Dessler at the behest of Jack's brother and the CEO of BXJ Technologies Graem Bauer; senior Executive of Omicron International; killed by Jack Bauer
- Brennan: head of the unit that infiltrated the Presidential Estate on Christopher Henderson's order to assassinate Wayne Palmer; was later present during the exchange between Henderson and Evelyn Martin; killed by Jack Bauer
- Cobb: one of the men in Brennan's squad; was knocked out by Wayne Palmer
- Henderson's mercenary: ran security during the exchange between Evelyn and Henderson
- Cooper: leader of Henderson's mercenary squad to assassinate Jack Bauer, Wayne Palmer, and Carl Mossman at the City Trust and Savings; Bauer tripped an alarm making LAPD arrive and engage Cooper and his men; Mossman and Cooper were killed in the ensuing gunfire with the LAPD and military as Bauer and Palmer eluded the scene
- Stipes: leader of the mercenaries who flew alongside James Heller's car in a helicopter with orders to kill him if Henderson did not periodically contact them; killed by Curtis Manning
- Henderson contact: intercepted a 911 call made by Amy Martin; reported this to Henderson
- Scott Evans: lead pilot for Omicron International; Henderson handed off the recording to him; forced by Jack to land his plan and later incarcerated
- (David Emerson: as revealed in Day 7, he was the leader of a group of Henderson's men who revived Tony Almeida less than 10 minutes after his heart was stopped by Henderson)
Charles Logan's cabal and supporters
The highest-ranking sponsors of the conspiracy, President Charles Logan and Graem Bauer.
President Charles Logan: a high level sponsor of the conspiracy; was exposed when Jack Bauer found a recording of a conversation between him and Henderson; after Miles Papazian destroyed this recording, Bauer, Chloe O'Brian, Mike Novick, Aaron Pierce, and Martha Logan worked together to expose him and remove him from office; arrested for murder and treason
- Walt Cummings: Logan's Chief of Staff; involved in the early hours of the conspiracy with Nathanson; killed but framed as a suicide under orders from Graem and his associates, who planned to have him be the scapegoat of the plan from the beginning
- Hank: an assassin hired by Cummings to eliminate Jack Bauer; failed, and killed by Jack; was entered into CTU by an unsuspecting Spenser Wolff
- Schaeffer: Cummings' inside man within the terrorists; exposed then killed by either Ivan Erwich or his men
- James Nathanson: Charles Logan's middleman and contact for Cummings; with the help of Russian Consul Anatoly Markov, he established communication with the separatists and supported Anton Beresch and his men; after being discovered, Nathanson cut a deal to gave Bauer a chip that lead to Omicron International and Henderson; killed by Ostroff's separatists
- Spotter: a field operative of Nathanson who found Haas and his three men dead and was the middleman for communications between Haas and Nathanson
- Conrad Haas: a trained sniper and assassin hired by James Nathanson and Christopher Henderson who killed David Palmer, bombed Michelle Dessler and Tony Almeida's car, and tried to kill Chloe O'Brian; killed in cold blood by Jack Bauer
- Kohler: one of the three men working beneath Haas; pursued Chloe O'Brian; was stabbed in the neck by Jack Bauer.
- Conrad Haas: a trained sniper and assassin hired by James Nathanson and Christopher Henderson who killed David Palmer, bombed Michelle Dessler and Tony Almeida's car, and tried to kill Chloe O'Brian; killed in cold blood by Jack Bauer
- Alpha 7: associate and co-conspirator of Nathanson; killed by one of Bierko's men
- Nathanson's man: one of the subordinates of Nathanson; killed by Ostroff while hunting for Nathanson.
- Spotter: a field operative of Nathanson who found Haas and his three men dead and was the middleman for communications between Haas and Nathanson
- Anatoly Markov: Russian consul; introduced during Day 6 when Logan revealed that he was a co-conspirator in the events leading up to Day 5; he was the operative inside the Russian government who helped Nathanson establish a connection with the separatists
- Justin Adams: a corrupt Secret Service agent loyal to President Logan; restrained Martha Logan; later was sent to murder Aaron Pierce, but was shot first by Martha Logan using his own gun
- Miles Papazian: Homeland Security staffer; allegedly sexually harassed Shari Rothenberg several years ago; destroyed an important and incriminating audio recording of President Logan to gain favor and was rewarded with the promise of a high-ranking position at the White House; fate unknown after Logan was arrested
BXJ Technologies cabal members
Graem Bauer: the leader of the four BXJ Technologies co-conspirators; directed President Logan through the cover-up in the last hours of the day; ordered Henderson to kill David Palmer and told Cheng Zhi that Jack is alive (after Logan's arrest, he was not implicated in the conspiracy and he remained at large; killed during Day 6 by his father Phillip)
- Ron: one of Graem's three co-conspirators at BXJ
- Robert Joseph: one of Graem's three co-conspirators at BXJ
- (Alan Wilson: revealed by Tony Almeida during Day 7 to have been a primary architect of the Sentox conspiracy as "the man behind Charles Logan"; his actual relationship to BXJ was not elaborated upon)
Chinese operatives
- Cheng Zhi: kidnapped Jack Bauer in recompense for Jack's invasion of a Chinese consulate during Day 4 and to extract American secrets from him
- Chinese agent: one of Cheng's men; deceived Jack Bauer to assist in his kidnapping
Miscellaneous
- Spenser Wolff: although well-intentioned, Wolff was unknowingly a mole in CTU planted by Walt Cummings to spy on Jack; through Wolff was Cummings able to get Hank into CTU
- Hervé: verified Collette Stenger's (later nullified) immunity deal that would've granted her full immunity for her terrorist collaborations