Son of David Sheridan, a diplomatic envoy, John Sheridan was born in North America in 2215. He loved adventures already at a young age and on his 21st birthday he ran off to attend the installation of the new Dalai Lama. Sheridan's first marriage three years later in 2239 was an equally quick decision. Fresh out of Officer Training School he married Elizabeth Lochley, but the marriage wasn't a successful one - after only three months later the two filed for a divorce having realized that neither one of them was mature enough for a marriage.

In 2236 Sheridan joined Earthforce in the hope that a military career would offer an adventurous life. His first assignment was on the Moon-Mars patrol where he served under Jack Maynard. Some years later he joined the crew of the Lexington. In 2245 he was offered an assignment as the XO of the Prometheus, a ship on a mission to make the first contact with the Minbari. Sheridan refused partly because he didn't trust the ship's captain and partly because he suspected that his father had arranged this promotion for him. He made the right decision - the Prometheus mission failed and was the sole cause for the Earth-Minbari War.

During the Minbari War Sheridan was forced to take command of the Lexington when the ship's captain was killed in a Minbari ambush. He and the rest of the crew survived only by chance as the Minbari though them to be dead. In order to keep on surviving Sheridan then had to come up a plan to defeat the enemy vessel, the Minbari flagship Drala'Fi. He succeeded and scored the only true victory that Earth was to have during the war. The Minbari considered his strategy - luring the ship into a mined asteroid field with a distress signal - a dishonorable one and gave him the name 'Starkiller'. Humans on the other hand naturally regarded him as a hero and he was later awarded with the Silver Star for Valor. Still, the war was not over yet. Sometime later Sheridan, alongside with Stephen Franklin and G'Kar, was assigned to represent Earth in a secret peace meeting organised by Delenn and Lennon, the current Ranger One. This last best hope for peace failed as the Centauri accidentally killed Lennon and the Minbari, unaware of Delenn and Lennon's plans, blamed the humans for his death. It was only a 'code word' which Lennon had taught Sheridan that saved him and Franklin from being executed.

After the war Sheridan was assigned to Io where he met Susan Ivanova. A few years later he served on Mars and helped to end the food riots there. Finally in 2253 he was promoted to the rank of captain and received a command of his own, the Galatea.

In 2249 Sheridan married for the second time, this time to his sister's friend, a xenoarcheologist called Anna. Both Sheridan and Anna had demanding jobs and this forced them to spend much of their time away from each other. Still, they were happily married for seven years. Their marriage came to a sad end soon after Sheridan had received the command of the Agamemnon. In 2257 the two were supposed to spend their seventh anniversary together, but troubles on the Agamemnon and Anna's two-week assignment on the research vessel Icarus changed their plans. While Sheridan helped to save Babylon 5 from an attack by the Home Guard, the Icarus was destroyed and Anna was presumed dead.

Sheridan buried his grief in work and for the next two years commanded the Agamemnon on deep space patrol until in January 2259 he was unexpectedly appointed as the new commander of Babylon 5. President Clark had chosen him in the belief that a hero of the Earth-Minbari war would make a better ally than the station's previous commander Jeff Sinclair who had been favoured by the Minbari. What Clark didn't know was that Sheridan was already working for a faction within EarthForce determined to find evidence of Clark's involvement in President Santiago's death.

Sheridan had a hard work ahead of him in not only running the station and keeping his anti-Clark contacts hidden, but also in gaining his co-workers' trust after Sinclair's surprise re-assignment. His first actions after coming to the station included promoting Ivanova and helping Franklin save Michael Garibaldi by donating his life-energy to the security chief with the Alien Healing Machine. In no time he had made friends with most of the command staff and eventually let them in on the conspiracy against Clark.

Sheridan also made friends with his non-human colleagues. When he was abducted by the Streib, Kosh Naranek contacted him through a dream and soon Sheridan began to notice that the ambassador was keeping an eye on him. Sheridan's sympathy towards the Narns gained him the trust of G'Kar, but the most surprising was perhaps his friendship with Delenn. The two had met briefly during the Earth-Minbari War (Delenn had been the high-ranking Minbari who had ordered him, G'Kar and Franklin to be released), but did not recognise each other. Still, less than a few months after their first meeting on B5 they were already having dinners and organising humanitarian aid to the Narns.

Towards the end of 2259 Sheridan found out that not all members of the crew of the Icarus were dead - at least one, Dr. Morden, had survived. Enraged he had Morden arrested and risked his career in trying to find out what had really happened to Anna. Realising that the Captain was close to discovering the existence of Shadows, Kosh and Delenn decided to invite him to the Army of Light and let him in on the truth about the fate of the Icarus. The ship had not been destroyed in an accident - the Shadows had captured the crew and killed those who would not serve them. Sheridan, sure that Anna would not have served and had thus been killed, swore to revenge her fate despite Kosh's warnings that should he go to Z'ha'dum he would certainly die.

Clark had made a mistake in assuming that Sheridan would support his actions and politics. Not only was the Captain involved in the conspiracy against Clark and allying himself with (wrong) aliens, but in December 2259 he openly defied Earth's decision to side with the Centauri during the Narn-Centauri war. This almost had Sheridan killed when a group of Centauri placed a bomb on the core-shuttle, forcing him to jump off. The only reason why Sheridan didn't end up as a part of the landscape was Kosh's decision to risk exposure and save him in the guise of an angel. The ambassador did this because he believed that Sheridan would have an important role to play in the next Great War.

In 2260 the clandestine conspiracies of the previous year began to come into the light. By now Sheridan had gained valuable allies in Kosh (who was teaching him how to fight the legends), Delenn (who shared the command of B5's Rangers with him), G'Kar (who offered him the help of all the Narns on B5) and Draal (who placed the Great Machine of Epsilon 3 at his disposal) and in January he was given the White Star prototype by the Minbari Religious Caste. These resources came in need in March when Sheridan and Delenn led the first attack against the Shadows (and Clark) by taking the White Star to Earth space and destroying the Shadow vessel Clark's forces had discovered on Ganymede. Less than a week later all hell broke loose.

Sheridan's allies had already some time earlier found the evidence needed to prove Clark's involvement in Santiago's murder, but Clark was still unaware of Captain's role in the greater scheme of things. Of course the Nightwatch had had its suspicions, but it wasn't until Sheridan declared B5 independent that Clark realised the mistake he had made in putting Sheridan into a position of power.

After a battle to retake B5 (won by Sheridan thanks to support from Delenn), Clark left the station alone and Sheridan was able to turn his attention back to the Shadow War. For a long time Delenn and Kosh had known that Sheridan would have a crucial role in the coming war, and by the end 2260, no one could have doubted it. He managed to persuade the warring League Worlds into joining their forces, and even stood up against Kosh when the Vorlons refused to do their part. The latter half of the year was filled with both victories (realising that telepaths could be used as weapons against the Shadows, completion of the whitestar fleet) and losses (the death of Kosh, Franklin's resignation), but the most curious interlude came when Sheridan took part in a mission to steal Babylon 4.

In August 2260 Delenn, Ivanova, Sheridan and Sinclair together with Marcus Cole, Lennier and Zathras travelled back in time and sent Babylon 4 thousand years into the past. It was during this mission that Sheridan - whose relationship with Delenn had slowly progressed from friendship to love - became 'unstuck in time' and found himself seventeen years into the future. It was a future where he and Delenn were married and had a son, but also a one where the war against darkness had not been completely won and the Centauri had paid a dear price for their co-operation with the Shadows. After returning to his own time Sheridan was stunned to hear the truth about the Minbari legend of 'The One' - namely that he was a part of it. He was 'The One Who Will Be' while Sinclair and Delenn, respectively, were 'The One Who Was' and 'The One Who Is'.

With the League of Non-Aligned Worlds behind him, Sheridan began taking the offensive against the Shadows. Unfortunately the Shadows had an ace in the hole - Anna Sheridan. She arrived to B5 in December 2260 and found her husband and Delenn in his quarters. Sheridan was shocked not only because of Anna's apparent return from the dead, but also because of the fact that Delenn had suspected she was alive and had not told him. Sheridan followed Anna to Z'ha'dum knowing that she was leading him to a trap - he knew that even though all tests indicated that she was who she claimed to be, her personality had been altered. The Shadows welcomed him amicably and tried to persuade him to change side. Sheridan wasn't convinced, though - he had seen what the Shadows did to those who would not serve. Remembering the future he had seen on B4 Sheridan decided to sacrifice his future with Delenn hoping that in the alternate future the Shadow War would be won and the Centauri would not have to suffer. He escaped the Shadow allies (Anna, Morden and an older man called Justin) and signalled the White Star (armed with two 500 megaton nuclear warheads) to collide with the Shadow base. He was prepared to die, but at the last moment he heard Kosh's voice in his head, urging him to jump into a bottomless pit. He did and lived at least a few seconds longer than Anna.

Sheridan woke up in the caves beneath Z'ha'dum accompanied by Lorien, an ancient being who claimed to be not just one of the First Ones, but the First One. Lorien told him that he was dead, trapped in between moments, in between life and death. The only way out was to surrender to death and perhaps, if Sheridan had something to live for, Lorien could bring him back to life.

Two weeks after his disappearance Sheridan returned to B5 accompanied by Lorien. Most of the aliens and humans on the station regarded Sheridan as a semi-god and the Captain took advantage of this to re-unite the League worlds who after his disappearance had began to doubt the necessity of a war against the Shadows. Still, Sheridan was by no means immortal. In fact, he only had twenty years to live. Shortened life-span gave Sheridan's cause more urgency and he became more determined than ever to win the war. Only days after returning to B5 he demanded Ulkesh, the Vorlon ambassador who had replaced Kosh, to leave the station because of the attacks the Vorlons had made against anyone who had had anything to do with the Shadows. Ulkesh refused and Sheridan had him killed.

Together with Delenn Sheridan brought together all the races who had signed on with the Army of Light thus creating the biggest fleet in history. They needed it if they were going to fight not only the Shadows, but also their former allies, the Vorlons. Sheridan had realised that the conflict between the two warring First Ones was not about power, but about philosophy - a battle between chaos and order. He made sure that during the last fight all three factions - the Shadows, the Vorlons and the Army of Light - were at the same place, namely Corianna 6, at the same time and thus were forced to confront each other directly. By contacting Sheridan and Delenn telepathically the First Ones tried one more time to persuade the younger races to choose sides. Sheridan had anticipated this and Lorien made sure that everyone on the battlefield saw the same thing Sheridan and Delenn did and in the end the First Ones were forced to surrender and leave beyond the Rim.

Even with the Shadow War over, Sheridan was not allowed to rest. Clark was still in charge of the almost totalitarian Earth and Sheridan took on the difficult task of uniting the bickering resistance groups. The Shadows had been Clark's allies and with them gone, the President turned his attention back towards B5. The station was put under an embargo and both Psi Corps and ISN were harnessed to fight the resistance. Sheridan's forces were able to get around the embargo by using their alien contacts and the black market and the attack by Psi Corps with the help of Bester, but the propaganda war by ISN hit them right where it hurts. The coverage ISN made of B5 claimed that Sheridan was a victim of 'minbariwar-syndrome' and a mere puppet of the alien governments. In response to these allegations Sheridan and Ivanova started the "Voice of Resistance", a propaganda-free news channel. Still, it wasn't until Clark had 10 000 refugees killed that Sheridan was forced to take the offensive against the President.

Sheridan's fleet - what was left of the White Star fleet combined with those Earth ships that had defected to the resistance - took one victory after another until Clark's allies found their Achilles' Heal - Sheridan's family. Ever since his return from Z'ha'dum Sheridan had been at odds with Garibaldi, suspecting that something was wrong, but dangerously unaware that his former friend and subordinate had allied himself with the enemy. In October 2261 Garibaldi, brainwashed by Bester and working for William Edgars, helped to set up a trap for Sheridan using his father as a bait. The trusting Captain believed his ex-chief of security and, despite of Ivanova's warnings, walked straight into an ambush.

After his capture Sheridan was taken to a prison in Syria Planum where he was interrogated and submitted to both mental and physical torture. Still, Sheridan didn't break and after a week of this hell he was, with the help of the Mars Resistance, rescued by Franklin, Lyta Alexander and Garibaldi (who by now had been released from Bester's command). The Captain resumed his place as the leader of the resistance just in time to hear both good and bad news from the front. The good news was that the alien governments had given their support to his cause; the bad news that Ivanova had been fatally wounded. Respecting the wish of his dying friend, Sheridan led the final assault on Earth in November from his old ship Agamemnon. Near Mars orbit his forces were able to cripple most of Earth's fleet and then advanced towards Earth itself. Realising his defeat Clark killed himself, but not before making an attempt to 'poison the wells' by turning the planetary defense grid against Earth. With the help of alien governments and ships loyal to Clark Sheridan was able to save Earth from annihilation.

With the Civil War now over, Sheridan had to return to Earth and take responsibility of his actions. He was regarded a hero by some and a traitor to Earth or at least a political nuisance by others. As a compromise Acting President Susanna Luchenko offered amnesty to him and all the soldiers under him in return for his resignation from Earthforce. The other choice being a military tribunal, dishonorable discharge and most likely a place at the wrong end of a firing squad, Sheridan had no choice but to accept the offer, but not before promoting Ivanova (who had survived thanks to Marcus and the alien healing machine) to the rank of Captain. Still, he wasn't unemployed for long - the League of Non-Aligned Worlds together with the Minbari, the Narn and the Centauri had already elected him as the president of the newly formed Interstellar Alliance.

After accepting the position and using it to fulfill his promise of an independent Mars, Sheridan returned to B5 and married Delenn. Although ISA intended to buy the station from Earth, Sheridan chose his ex-wife Captain Lochley (who had been loyal to Clark during the war) to command the station. Still, he remained the highest authority in matters that concerned the ISA. Sheridan and Lochley's opinions clashed almost immediately when Sheridan allowed a group of telepaths form a colony on station despite of Lochley's objections. When the telepaths began to demand a homeworld of their own, black-mail ambassadors and cause violence, Sheridan was forced to take back the protection he had promised them. Still, the damage had already been done and the situation snowballed into a hostage crisis and the martyr death of the telepath leader Byron (which in return sparked off the Telepath Crisis a few years later). At same time another war was brewing - an unknown party was randomly terrorising the Alliance shipping routes leaving the member worlds blaming each other.

After a long investigation, the Alliance discovered water-proof evidence that the Centauri were behind the attacks. Having promised the member worlds his support no matter who the guilty party was, Sheridan was now forced to put an embargo on a world that had supported him during the Civil War. To prevent any more violence, he ordered the whitestar fleet to act as a buffer between the Centauri and the other races. Unfortunately Garibaldi, now ISA's Head of Covert Intelligence and responsible for keeping the whitestar fleet informed, was drunk at a crucial moment and the Centauri declared a war against the Alliance. Even with a full-grown war in his hands Sheridan refused to authorise the bombing of civilian targets, namely Centauri Prime itself. Tired of Sheridan's messianic approach to politics the Drazi and the Narn then organized an attack against the Centauri capital. After Sheridan found out about this bloody breach of protocol he travelled to Centauri Prime himself, but arrived there too late to prevent the bombings. The war did end at this attack, though. Londo Mollari, now the emperor of his people, contacted Sheridan blaming the late Regent for the original terrorism that had started the whole thing and reluctantly promising that the Centauri would pay reparations for the Alliance. Sheridan accepted Londo's peace offering unaware that the Drakh were the true puppetmasters and that he had taken yet another step towards the future he had seen on B4 two years earlier.

Conflicts within the Alliance were not Sheridan's only problem - the whitestar fleet had been reduced dangerously small during the last three wars. In order to maintain the necessary superior force in arms, Sheridan took on to himself to form an industrial alliance between ISA, Earth and Minbar, that would result a new and more powerful whitestar fleet.

In late 2262 the new headquarters for the Alliance were finally finished and Sheridan had to bid farewell to B5 which had been his home for the last four years. Moving to Minbar wasn't the only major change in his life, though - Delenn was pregnant and he would became a father. The moving itself wasn't uneventful either. There was a coolant leak on the whitestar taking them to Minbar and Sheridan and a Ranger were left trapped in a room that was filling with a poisonous gas. Lennier witnessed the accident, but instead of letting the men out, he chose to leave them to die. By using the denn-bok of the unconscious Ranger Sheridan managed to break the glass doors and save them both. Despite what Lennier had done, Sheridan decided not blame him and kept the whole incident a secret.

On Minbar Sheridan and Delenn were surprised to find Londo waiting for them. The last time they had met with the Emperor he had been rallying his people against the Alliance and now he was even presenting a gift, an ancient urn, to their unborn child. The innocent-looking gift cast a dark shadow, though. It contained a keeper which would take control of the child on his 16th birthday.

The co-operation between Earth, Minbar and the Alliance eventually resulted the birth of a new class of ships and two prototypes, Victory and Excalibur, were constructed in secret and finished in 2267, just before the fifth anniversary of the Alliance. When Sheridan visited the ships for the first time, the Techno-mage Galen contacted him through a dream. The mage warned him of a Drakh plan to destroy Earth and told him to find the three other people who could help him to prevent this. Sheridan followed Galen's instructions and eventually hijacked the two prototypes in order to stop the Drakh. He and his allies managed to destroy the Drakh's main weapon, the death cloud, but the retreating Drakh were able to infect Earth with a biogenetic plague.

Despite their initial suspicions and occasional back-occasional, the Alliance worlds eventually began to appreciate the work Sheridan had done for them. The Interstellar Alliance had brought peace, prosperity and stability to the galaxy and so Sheridan, the personification of the Alliance, was re-elected again and again. He himself tried to persuade the member worlds to at least consider an open election with more than one candidate, but even this didn't lessen his popularity. He wasn't without enemies, though. The Drakh were still holding the reins on Centauri Prime, planning a war against the Alliance. Sheridan was aware of the warmongering, but dangerously unaware of who was doing it. In 2277 he found out.

Fifteen years after Londo's visit to Minbar, the Drakh keeper that had been waiting dormant inside the Centauri urn, took over Sheridan and Delenn's teenage son David. Under the influence of the keeper the boy then attacked his father, stole a shuttle and travelled to Centauri Prime. In order to save their son Sheridan and Delenn followed David there and were imprisoned by the insane Prime Minister Durla. Fortunately for them and David, Londo decided to intervene at the expense of his own life. The Drakh had ordered him to have the presidential couple executed, but instead he organised their escape. Thanks to the Centauri resistance organisation Legions of Fire, led by Vir Cotto, the Drakh were soon defeated and David was freed from under the influence of the keeper.

The whole business with the Drakh made Sheridan realise the fact that his life was nearing its end. In 2279 he resigned as the President of the Interstellar Alliance and Delenn was elected as his follower. In her new position Delenn couldn't spare the time to continue as Ranger One and she, in return, transferred this job to Sheridan. Two years later, in 2281, Sheridan's lease on life finally came to an end. After saying goodbye to his friends and family he took one of the whitestars and left Minbar to find his destiny in the stars. He visited B5 - now redundant and just days away from being demolished - for the last time before setting course to Corrianna 6 where the Shadow War had been won twenty years earlier. At the moment of his death he was visited by Lorien who took him beyond the Rim. A few days later the rangers discovered Sheridan's whitestar. All of the ship's airlocks were sealed, but Sheridan's body was nowhere to be found and some Minbari believe that one day Sheridan will return.