President of the High Council

The President of the Supreme Council of Gallifrey and All Her Dominions, Holder of the Wisdom of Rassilon, Preserver of the Matrix, Guardian of the Legacy of Omega, often simply Lord President or Lady President, governed the High Council of Time Lords, making him or her the holder of the most powerful office on Gallifrey. (AUDIO: The Inquiry)

Alternatively, the Seventh Doctor once introduced himself as President-elect of the High Council of Time Lords, Keeper of the Legacy of Rassilon, Defender of the Laws of Time, Protector of Gallifrey. (TV: Remembrance of the Daleks)

Prerogatives
The ceremonial privileges of the President included access to the APC Net by means of the Matrix Crown (TV: The Invasion of Time) and the possession of the Sash and Rod of Rassilon. (TV: The Deadly Assassin) Donning the sash also affected a permanent change to the biodata of the Time Lord who wore it as President, providing the Doctor and others with access to secret biodata codes that would grant access to some of the Time Lords' greatest and most powerful secrets. (PROSE: Alien Bodies)

The President also had the formal responsibility, not attempted in reality except by the Fourth Doctor, to seek the Great Key of Rassilon — a separate artefact from the Rod of Rassilon, which was also sometimes referred to as the Key of Rassilon. (TV: The Invasion of Time)

The Lord President could not be put on trial, (TV: The Mysterious Planet) but he or she could certainly be called to give evidence in a judicial investigation. (AUDIO: The Inquiry)

When Romana II's presidency was impeached and she was nearly deposed, in her present incarnation she wasn't permitted to contest the presidency against Inquisitor Darkel and Lord Cardinal Matthias, but she said she would go under voluntary regeneration and contest it in her next incarnation. This didn't happen as she wasn't deposed. (AUDIO: Appropriation)

Holders of the office of president
Rassilon was the first President and founder of modern Time Lord society. (TV: The Five Doctors)

Pandak was one of the early Time Lord Presidents and one of the founders of Time Lord society. (PROSE: Lungbarrow, PROSE: The Ancestor Cell) Several later Presidents were named after him, (PROSE: Lungbarrow) including Pandak III, who at one point ruled for over 900 years. (TV: The Deadly Assassin)

Pandora was the first female President. She was overthrown by her High Council after claiming the title of Imperiatrix. (AUDIO: Lies)

According to a nightmare the Fifth Doctor had under the influence of the Celestial Toymaker, Drall was President during the First Doctor's time at the Academy. (PROSE: Divided Loyalties)

A male President changed the Constitution of the Time Lords to enable the President to name his own successor. That President's grandson, Pundat the Third, himself became a corrupt President, and was succeeded by Slann, who was President at the time of the Doctor's departure from Gallifrey, and was assassinated by the Master. (PROSE: Birth of a Renegade)

According to another source, President Pandad VII ordered Irving Braxiatel, then Lord Burner, to burn "an old man" and "his granddaughter" from history. Braxiatel disobeyed this order, and the intended victims stole a TARDIS and fled Gallifrey. The very same day, President Pandad died when a power relay in his office overloaded; an inquiry headed by Braxiatel found that this was an accident. (AUDIO: Disassembled)

Morbius was a president who led a war of conquest. He was overthrown by the High Council. (TV: The Brain of Morbius) Saran was Morbius' Vice President and became President after his expulsion from Gallifrey. (PROSE: Warmonger)

A male President ruled when Omega tried to return by draining power from Gallifrey. (TV: The Three Doctors) Perhaps the same popular-yet-unnamed male President resigned from the position after a term of office that was short in comparison with the 900-year precedent set by Pandak III. However, before he could name his successor, he was assassinated by Chancellor Goth, who was plotting with the Master to frame the Fourth Doctor and take power uncontested. The Doctor ran against Goth in the election to buy himself time to investigate the death; he succeeded in unraveling the scheme, but in the process, the Master killed Goth, leaving the Doctor as the next President. Because the Doctor didn't want this responsibility, he left in his TARDIS. (TV: The Deadly Assassin)

Despite his total lack of intent to seriously become President, Greyjan the Sane was left in charge after the two other candidates unexpectedly withdrew from the race. His Presidency lasted for only three years before he killed himself. During those three years, Faction Paradox purchased the eleven days between the 2nd and 14th September 1752. (PROSE: The Ancestor Cell)

When the Fourth Doctor returned to Gallifrey, finding the planet without a President and led by Lord Chancellor Borusa, he claimed his right to the Presidency from the old election, and he briefly became the 407th President (TV: The Invasion of Time, PROSE: The Ancestor Cell) before surrendering the title and leaving again. (TV: The Invasion of Time) The Fifth Doctor later discovered that this short term had been officially stricken from the record, (AUDIO: Time in Office) though it was known to students on Gallifrey shortly before the outbreak of the War. (PROSE: The Ancestor Cell)

Borusa served as President after the Doctor resigned from his role, (TV: The Invasion of Time, Arc of Infinity) but he eventually fell from grace when the stress of his new position drove him insane, causing him to seek the secret of immortality from Rassilon. This ended when Rassilon turned Borusa into living stone. (TV: The Five Doctors)

After Borusa's apparent disappearance, the High Council appointed the Fifth Doctor to be his successor, (TV: The Five Doctors) and though he tried to evade his role as President, he was eventually forced to take on the responsibilities, and he enacted several political reforms before appointing Lowri as his acting successor and leaving again to travel. (AUDIO: Time in Office)

Flavia was appointed as acting President by the Fifth Doctor when he chose to depart Gallifrey, before she was overthrown in favour of Niroc, a puppet of the Celestial Intervention Agency who oversaw Operation Ravolox and the Sixth Doctor's trial. (PROSE: The Eight Doctors) Flavia was again President for a period, then challenged and beaten for presidency by Romana II. (PROSE: The Eight Doctors, Happy Endings)

A male President served as interim president during Romana II's imprisonment by the Daleks, (AUDIO: The Apocalypse Element) and was involved in the affair of the Sirens of Time before it was erased from history. (AUDIO: The Sirens of Time) Another male President ruled for a time, sending Straxus on a mission to World War I. (AUDIO: X and the Daleks)

Romana II and Pandora (inhabiting the body of Romana's first incarnation) both claimed the title of Imperiatrix when Darkel invoked a "right of challenge" for the Presidency. (AUDIO: Imperiatrix) After Pandora's defeat, Valyes became acting President while Romana was incapacitated; upon his resignation, Darkel, Matthias, and Romana each claimed the Presidency. (AUDIO: Appropriation) Despite this, the title went to Irving Braxiatel, who extremely quickly named Matthias his successor and resigned. (AUDIO: Mindbomb) Matthias saw Gallifrey almost destroyed by the Free Time Dogma Virus, (AUDIO: Mindbomb, AUDIO: Panacea) and after his efforts forced him to resign, Romana II returned to office. (AUDIO: Ascension)

Romana II regenerated while trying to stabilise the engines of the Moros, (AUDIO: Enemy Lines) and Romana III was President during the rise of the Adherents of Ohm. (AUDIO: Intervention Earth) In preparation for the subsequent war, (AUDIO: Enemy Lines) she declared herself War Queen and constructed nine decoy Gallifreys to distract the enemy. (PROSE: The Shadows of Avalon)

During an invasion of Romana's Gallifrey by a far-future sect of Faction Paradox, Greyjan the Sane was resurrected to challenge her rule, and the Eighth Doctor destroyed the planet. (PROSE: The Ancestor Cell) Many other decoy Gallifreys were destroyed during the War in Heaven. (PROSE: Alien Bodies, The Taking of Planet 5, The Brakespeare Voyage)

On another Gallifrey, perhaps the original, (PROSE: The Taking of Planet 5) an obstructionist President took charge. This President was killed while trying to prove the nonexistence of the enemy, leaving the useless Umbaste in charge. (PROSE: The Book of the War) At one point, this Lord President was briefly incapacitated and appointed Voran to be Acting President in his stead. (PROSE: The Infinity Doctors) Finally, Umbaste committed apparent suicide and was replaced by the reformed renegade who first warned the Great Houses about the enemy. This renegade declared himself the War King and led the Homeworld through the first fifty years of the War in Heaven. (PROSE: The Book of the War)

Sometime after the War's fiftieth year, (PROSE: The Book of the War) the War King started losing his power over the War Council, and ultimately he was deposed when the 101-form timeship Lolita gained popular support and killed him by absorbing him into her interior dimensions. (AUDIO: Body Politic) However, Lolita's rule ended shortly afterwards, when Horus led an army of Osirians to invade the Capitol and kill her. (AUDIO: The Judgment of Sutekh)

As the Doom Coalition began to put their plans into actions in destroying the future, Padrac became President for a short while, before the Coaltion's plans were stopped by the Eighth Doctor, Liv Chenka and Helen Sinclair. (AUDIO: Songs of Love, Stop the Clock)

Before her death, Romana III sent Irving Braxiatel into her past to undo her regeneration on the Moros. After he rescued Romana II, he persuaded her to prevent the war by stepping down from the Presidency and appointing her political opponent Livia as her successor. (PROSE: Enemy Lines) However, this did not stop war from coming: at the start of the Last Great Time War, Livia stepped down and orchestrated Valerian's rise to power, despite Romana II's candidacy in the election. When a video of Romana making a deal with the Dalek Emperor was uncovered, Valerian was elected Lord President, and in fulfillment of Livia's plans, Rassilon was resurrected into his body. (AUDIO: Desperate Measures)

Rassilon was still President through the end of the Time War, (TV: The End of Time, PROSE: Engines of War) and he led Gallifrey's return to the end of the universe, but, upon the Twelfth Doctor's arrival on the planet, he was overthrown and banished, along with the rest of the High Council, due to his role in Clara Oswald's death.

Following this coup, the Twelfth Doctor became Lord President of Gallifrey himself. However, this coup was a ruse in order to gain access to a Time Lord extraction chamber to save Clara's life, and he quickly fled Gallifrey in a stolen TARDIS, abandoning the title yet again. (TV: Hell Bent) A female President succeeded the Doctor, inheriting Rassilon's gauntlet, but her reign was cut short when Gallifrey was invaded by Cybermen led by Rassilon, who killed her with a staser before reclaiming his gauntlet and title of Lord President. Due to the Doctor and Rassilon reversing these events, this President was restored to life. (COMIC: Supremacy of the Cybermen)

Alternate timelines
In an alternate timeline, the Sixth Doctor was Lord President Admiral of Gallifrey in the War against the Enemy, who were being aided and abetted by the Master. (PROSE: The Quantum Archangel)

In a timeline in which it was standard policy for the Time Lords to sell their temporal technology to the highest bidder and regenerations could be extracted and sold, Leela and K9 Mark I accompanied the Fourth Doctor on his search for the Key to Time. She was the only human to hold the Key to Time in her hands. Consequently, when Leela's counterpart from the proper timeline visited this alternative Gallifrey, she was appointed Lady President. (AUDIO: Reborn)

In a timeline in which the Time Lords regularly altered history through the Temporal Intervention Agency, Romana II became Lady President as in the proper timeline but was considerably more ruthless than her counterpart. Her Interrogator General was Leela, who murdered her predecessor Narvin to achieve the position, while the Doctor, by then in his sixth incarnation, served as Lord Burner, the President's personal temporal assassin who "burned" people from history. Vansell served as Castellan. (AUDIO: Disassembled)

In a timeline in which Rassilon failed to finish the Eye of Harmony before his death, Romana II reigned as Lady President over a Gallifrey which never achieved time travel and where slavery still existed. She was assassinated on the orders of Lord Chancellor Narvin but was immediately replaced by her counterpart from the proper timeline, who claimed that the victim of the assassination was a decoy. After the alternative Narvin was killed by the Krilig, the Narvin from the proper timeline assumed his identity. (AUDIO: Forever)

In an alternate timeline in which the Daleks were peace-loving academics and friends of the Time Lords, a Lord President was cured by Dalek surgeons who removed a microaneurysm from his brainstem. (PROSE: The Ripple Effect)

In an alternate timeline in which the Doctor never left Gallifrey, Susan Foreman ran for the presidency. (AUDIO: Auld Mortality) She won the election after the Doctor left Gallifrey. (AUDIO: A Storm of Angels)

Presidente de Gallifrey