Timeline

The recorded history of Westeros extends back over 12,500 years, according to tradition, though the accuracy of the legends and myths that recount much of this history is openly questioned by the maesters of the Citadel, amongst others.

The Dawn Age

 * Prehistory: Westeros is ruled peacefully by the Children of the Forest, a dimunitive species of greenseers and wood-dancers.
 * c. 12,500 Before Aegon's Landing: A human ethnic group, the First Men, invades Westeros across the Arm of Dorne, bearing weapons of bronze. The Children of the Forest destroy the Arm with magic, creating the island chain known as the Stepstones, but the First Men are able to reinforce by ship. A fierce battle for control of Westeros begins. After years of warfare, the two sides agree to a truce, signing the Pact on the Isle of Faces. The First Men take control of the open lands and the Children take control of the forested interiors. In time, the First Men adopt the worship of the Old Gods of the Forest.

The Long Night

 * c. 8,000 BAL: A great winter that lasts a generation descends on Westeros, followed by a night that goes for years. Under the cover of darkness, the White Walkers invade Westeros from the uttermost north, causing immense suffering and destruction. In the War for the Dawn, the Children and the First Men unite to defeat the Walkers, eventually throwing them back into the north. In the eastern tradition they are led by a great hero of the east, a warrior named Azhor Azhai wielding a sword of fire named Lightbringer, but Westerosi accounts do not mention him. A great leader named Brandon Stark raises the Wall with artifice and magic to bar against the Walkers' return. He also founds the castle of Winterfell, founds House Stark and the Night's Watch and, according to some, is named as the First King in the North. Despite their victory, the Children of the Forest has been badly blooded in the war and begin to disappear from Westeros.

The Andal Invasion

 * c. 6,000 BAL: A race of men from Essos, the Andals, cross the Narrow Sea in numerous ships and make landfall in the Vale of Arryn. Under the banner of the Faith of the Seven, riding horses and wielding weapons made of iron, they overrun and conquer all of Westeros south of the Neck. Their attempts to invade the North are frustrated by the North's natural defenses, namely the swamps of the Neck and the formidable fortress of Moat Cailin, so eventually they make peace with the King in the North. A shifting quilt of small kingdoms take shape in southern Westeros.
 * c. 5,000 BAL: By this time the Andal occupiers and native First Men of the Iron Islands have intermingled to form a distinct new group, the ironborn. The ironborn reject the worship of both the Old Gods and the Seven in favor of their own deity, the Drowned God.

The rise and fall of Valyria

 * c. 5,000 BAL: On the eastern continent, the peaceful sheep-herding folk of the peninsula of Valyria find dragons lairing in the Fourteen Fires, an immense chain of volcanoes extending across the neck of the peninsula. The Valyrians tame the dragons with magic and begin expanding their influence. They fight five great wars against the Ghiscari Empire before finally throwing them down in defeat, expanding the Valyrian Freehold to include all of Slaver's Bay.
 * c. 1,700 BAL: The Valyrian Freehold begins settling the region of the modern Free Cities. Their expansion brings them into conflict with the native inhabitants of the region surrounding the River Rhoyne. Nymeria, the warrior-queen of the Rhoynar, realizes that they cannot stand against dragons and they flee to Dorne, in southern Westeros. There Nymeria marries Lord Mors Martell and helps House Martell conquer the rest of Dorne, finally unifying the region as one kingdom.
 * c. 500 BAL: A religious sect, the Moonsingers, leads refugees from the Valyrian-controlled areas of western Essos to a secretive lagoon protected by mountains and narrow access channels. Here they found the Secret City of Braavos.
 * c. 200 BAL: The Valyrians annex Dragonstone, an island in the Narrow Sea just off the eastern coast of Westeros. The Targaryen family takes control of the island, which is used as a trading post with the Seven Kingdoms. According to legend, Aenar Targaryen had a vision of impending catastrophe and arranged to have his family removed from the Freehold.
 * c. 100 BAL: The Doom of Valyria takes place. The Fourteen Fires erupt in a titanic explosion that obliterates the heartland of the Valyrian Freehold. Most of the Valyrian dragons, who lair in the volcanoes when not needed, are killed outright. The City of Valyria is partially buried under vast amounts of ash. The Valyrian Peninsula fractures and breaks apart. A large part of it is torn away from the mainland, low-lying areas are flooded and many offshore islands are formed. The waters around Valyria remain poisonous until the present day. In the aftermath of the Doom, many of the colony-states begin breaking away and asserting their independence, triggering a period known as the Bleeding Years. The Ghiscari empire begins a slow return to power. The Free Cities become free in truth. Braavos reveals itself to the outside world. The horselords of the interior plains, the Dothraki begin raiding surrounding lands at will, no longer constrained by the power of Valyria.

The Seven Kingdoms

 * c. 700-1 BAL: By this time, the numerous small kingdoms of Westeros have consolidated into several powerful nations. When the Stormlands successfully invades and conquers the Riverlands, this reduces the number of nations to seven: the Kingdom of the North, the Kingdom of the Vale, the Kingdom of the Isles and Rivers, the Kingdom of the Rock, the Kingdom of the Reach, the Storm Kingdom and the Kingdom of Dorne.
 * The Iron Islands conquers the territory of the Riverlands from the Stormlands. The ironborn king, Harren Hoare, also called Harren the Black, demonstrates his wealth and power by building a castle far vaster and more formidable than any other in all of Westeros, Harrenhal, a fortress almost completely impregnable to ground attack.

The Conquest

 * 1 AL: Despite pleas to intervene in the Free Cities, Aegon the Conqueror, the ruler of House Targaryen, decides to invade Westeros, along with his sister-wives Rhaenys and Visenya. With only a small number of soldiers, his forces make landfall at the mouth of the Blackwater Rush. On a tall hill overlooking the bay, he builds a wooden redoubt on the site of what is now the Red Keep. He then begins his military campaign using his secret weapon: the only three dragons known to have survived the Doom. The construction of Harrenhall castle finishes the same day that Aegon lands in Westeros.  When King Harren the Black refuses to surrender, Aegon uses his dragons to overcome Harrenhal's defenses and burns Harren alive in what is later called Kingspyre Tower. The remaining ironborn flee back to the isles and capitulate to Aegon, naming Vickon Greyjoy of Pyke to rule over them. Aegon is joined by Lord Edmyn Tully of Riverrun, who leads a popular rebellion of the rivermen against the ironborn. Aegon rewards Tully by naming him overlord of the Riverlands. Aegon's army then defeats the allied forces of King Mern IX Gardner of the Reach and King Loren Lannister of the Rock on what becomes known as the Field of Fire, as more than 4,000 men are burned alive by the dragons. House Gardner is extinguished, so Aegon names the stewards of Highgarden, House Tyrell, as overlords of the Reach. King Loren surrenders to Aegon, who names him overload of the Westerlands and allows House Lannister to continue its rule. Aegon's bastard half-brother, Orys Baratheon, kills the Storm King, Argilac the Arrogant, and seizes his castle of Storm's End, along with his daughter whom he takes to wife. Aegon rewards Orys by naming him overlord of the Stormlands and allowing him to found House Baratheon. Aegon is then legitimised when he enters the city of Oldtown and his war is blessed by the High Septon of the Faith of the Seven. King Torrhen Stark of the North also bows the knee, as does King Arryn of the Vale, but Aegon's attempt to conquer Dorne is thwarted by the Dornish refusal to give battle openly, preferring guerrilla warfare. Aegon decides to allow Dorne to remain independent and returns to the site of his landing to found the city of King's Landing.

The Targaryen Dynasty

 * 37-48 AL: Upon Aegon I's death, his son Aenys, born of incest, takes the throne. The Faith of the Seven rejects his legitimacy to rule and the Faith Militant lead a popular uprising against the Targaryens. The weak and indecisive Aenys makes his half-brother Maegor the Hand of the King and gives him authority to deal with the crisis. Maegor's response is bloody and ferocious, resulting in the deaths of thousands in battle, slaughter and dragonfire. The slaughter lasts all of Aenys and Maegor's reigns.
 * 48 AL: Aenys's son, Jaehaerys, becomes king. Jaeharys declares a truce and agrees to end the slaughter in return for the Faith Militant disbanding and accepting (but not approving) the Targaryen practices of incest and polygamy. They agree, and the Faith and the Throne are reconciled. Jaeharys I becomes known as the Conciliator for his ability solve crises without the need for violence.
 * 129-131 AL: The first major civil war in the history of the unified Seven Kingdoms. Upon the death of King Viserys I Targaryen, the Lord Commander of the Kingsguard, Ser Criston Cole, names Viserys's son Aegon II as King, despite Viserys's command that the crown be passed to his eldest child, his daughter Rhaenyra. The resulting war pits brother against sister and dragon against dragon in the war known as the Dance of Dragons. Aegon II's dragon consumes Rhaenyra, but the war continues in the name of her son, Aegon III. The death of Aegon II resolves the war, since Aegon III is the only heir to both of the combatants. The conflict is costly, with most of the Targaryen dragons being killed in the fighting. The last surviving Targaryen dragon, a sickly green runt, dies during Aegon III's reign, earning him the nickname 'Dragonbane'.
 * 157-161 AL: The reign of the Boy King, King Daeron I, who takes the throne at the age of fourteen and almost immediately launches an invasion of Dorne. Daeron's military genius is notable and he eventually forces the Submission of Sunspear. Unfortunately, he leaves a Tyrell of Highgarden, who have warred with the Martells for a thousand years, in charge. Tyrell's tyranny triggers an uprising against the Iron Throne. When Daeron I returns with a fresh army, he is killed, his cousin Prince Aemon the Dragonknight is captured and his army defeated. Daeron's brother and the new king, Baelor I, forges a peace treaty with Dorne (including the marriage of his second cousin Daeron to Princess Myriah Martell).
 * 161-171 AL: The reign of King Baelor the Blessed, the Septon King. Baelor is pious and holy, keeping the realm at peace. Upon his death, a huge new sept he is building in King's Landing is named the Great Sept of Baelor in his name.
 * 172-184 AL: The reign of King Aegon IV, Aegon the Unworthy, held to be the worst king in the history of Westeros. A glutton and a cruel, petty man, Aegon has a total of nine mistresses he keeps at court, to the dismay of his sister-wife Naerys. He holds his son and heir, Daeron, in disfavor due to his Dornish wife and peaceful ways, and gives a Valyrian steel blade of House Targaryen, Blackfyre, to his bastard son Daemon, whom he thinks is more martial and worthy of it. Upon his death, Daeron II succeeds to the Iron Throne.
 * 195-196 AL: Claiming that Daeron II is actually the product of an illegitimate relationship between Queen Naerys and her other brother, Prince Aemon the Dragonknight, Daemon Blackfyre claims the Iron Throne. Half the realm declares for him and the resulting civil war is known as the First Blackfyre Rebellion. This is a brutal and bitter conflict that kills many tens of thousands. Eventually, Daemon amasses enough strength to march on King's Landing, allied to the forces of his bastard half-brother Aegor 'Bittersteel' Rivers. Daeron II's sons, Baelor and Maekar, lead an army to stop him, assisted by another of Aegon IV's bastards, Brynden 'Bloodraven' Rivers. The resulting engagement, the Battle of the Redgrass Field, is one of the largest battles fought in Westerosi history. Bloodraven slays Daemon Blackfyre with arrows and then fights Bittersteel in single combat. The arrival of a Dornish army in support of the King routs the Blackfyre forces. Bittersteel flees the field with Daemon's surviving sons, taking them to safety in the Free Cities.
 * 197 AL: In thanks for the Dornish assistance on the Redgras Field, Daeron II marries his younger sister Daenerys to Prince Maron Martell, formally bringing Dorne into the Seven Kingdoms. Due to the peaceable union, Dorne is allowed to maintain a number of its own customs, including allowing women equal inheritance rights and the ruler of Dorne is allowed to retain the title 'Prince'.
 * 209 AL: The Great Spring Sickness tears through Westeros, killing King Daeron and most of his heirs. Aerys I Targaryen becomes king. He names Bloodraven as his Hand.
 * 211 AL: Blackfyre loyalists attempt to launch a Second Blackfyre Rebellion, but Bloodraven exposes the plan, captures one of Daemon Blackfyre's sons and executes many of the conspirators before a battle needs to be fought.
 * 221 AL: Maekar I becomes King of the Seven Kingdoms.
 * 233 AL: Maekar I dies fighting an outlaw knight. With his eldest two sons dead (one from a pox and one from drinking wildfire in a fit of madness), the council offers the crown to Maekar's third son, a maester of the Citadel. He refuses and removes himself to the Wall. Maeker's fourth son takes the throne, becoming Aegon V Targaryen, Aegon the Unlikely, the fourth son of a fourth son. During his reign Bloodraven is exiled to the Wall for reasons unclear to history.
 * 233-259 AL: The rule of Aegon V. This is a period of peace and plenty for the Seven Kingdoms. During the last year of Aegon V's reign, Pycelle is named as Grand Maester.
 * 259 AL: King Aegon and his son Prince Duncan are killed in a great fire at Summerhall, the Targaryen summer palace, apparently during an attempt to hatch the last three dragon eggs left in the west. Aegon's son, Aerys II Targaryen, becomes king. The eggs are assumed destroyed in the fire.

The Reign of the Mad King

 * 259 AL: King Aerys's reign begins with great promise. He sweeps aside the old men of his father and grandfather's courts and replaces them with young, vigorous replacements. He names the young Lord Tywin Lannister of Casterly Rock as his Hand, impressed with Tywin's ruthlessness in destroying two vassal houses which had refused to pay their taxes.
 * 260 AL: Maelys Blackfyre, the last of the Blackfyre Pretenders, plans to invade Westeros from a base in the Stepstones but Aerys sends an army against him in a preemptive attack. In the resulting War of the Ninepenny Kings, Maelys is killed by a promising young knight named Barristan Selmy. During the war Hoster Tully of Riverrun makes the acquaintance of a Baelish of the Fingers, later accepting his son Petyr as a ward at Riverrun.
 * 270s AL: Cracks begin to appear in Aerys's demeanor. He refuses to marry his son Rhaegar to Tywin's daughter Cersei, instead having Rhaegar marry Princess Elia Martell of Dorne. Aerys becomes paranoid over talk in the castle that Tywin is the true ruler of the Seven Kingdoms. When Lord Darklyn of Duskendale refuses to pay his taxes, Aerys resolves to crush the problem himself without Tywin's aid. Unfortunately, the situation gets out of control and Aerys is imprisoned for several months in Duskendale before Tywin and Barristan Selmy assault the castle and rescue him. The Darklyns are burned alive for their treachery. Later historians claim that the Defiance of Duskendale marked the beginning of the end for Aerys's sanity.
 * c. 280 AL: In a year of false spring, a great tournament is held by Lord Whent at Harrenhal. King Aerys and Prince Rhaegar attend, as do many lords from across the Seven Kingdoms. Prince Rhaegar wins the tournament, but names Lyanna Stark of Winterfell as the Queen of Love and Beauty rather than his own wife Elia. Lord Tywin Lannister is enraged when Aerys names his son Jaime to the Kingsguard, disinheriting him as Tywin's heir in favor of his ugly, misshapen younger brother Tyrion. Furious, Tywin resigns the Handship and returns to Casterly Rock. Some time later, Rhaegar allegedly kidnaps Lyanna against her will and disappears with her. Lyanna's brother Brandon and father Lord Rickard demand justice from King Aerys, but he has Rickard burned alive and Brandon strangled to death for daring to question what the Targaryens would choose to do.

Robert's Rebellion

 * 280-281 AL: In response to the king's murder of Rickard and Brandon Stark, the new Lord of Winterfell, Eddard Stark, raises the banners of the North. Robert Baratheon, Lord of Storm's End and betrothed to Lyanna, joins the rebellion, raising the banners of the Stormlands. Lord Jon Arryn of the Vale, a mentor to both Robert and Eddard, does the same. Lord Hoster Tully of Riverrun, who had planned to marry his daughter Catelyn to Brandon Stark, instead agrees to marry her to Eddard in exchange for his support in war. In addition, he marries his second daughter Lysa to Jon Arryn to shore up the alliance. The Stark, Tully and Arryn armies begin gathering north of the Trident, but Robert's forces are cut off far to the south. Leaving his brother Stannis to hold Storm's End, Robert marches his army north-west through enemy territory. He is defeated at the Battle of Ashford by Tyrell forces loyal to the king, but manages to cross the Trident and link up with the other rebels. Whilst Lord Mace Tyrell besieges Storm's End for a year, Prince Rhaegar leads a royalist army to directly engage the rebels, but is defeated at the Battle of the Trident and killed in battle by Robert. Lord Tywin's army arrives at King's Landing to defend the city, but once the gates are opened the Lannisters sack the city brutally. Aerys II is killed by Jaime Lannister, whilst Targaryen loyalists smuggle his surviving children Viserys and Daenerys to safety in the Free Cities. Robert Baratheon, due to a blood relationship with House Targaryen, is proclaimed King of the Seven Kingdoms. With Lyanna dead from a fever, Robert instead marries Cersei Lannister to shore up the alliance that brought down the Targaryens.

King Robert's Reign

 * 289 AL: Lord Balon Greyjoy leads a rebellion against King Robert's reign. After several months of furious fighting in the Westerlands and Riverlands, King Robert's forces push the ironborn back to Pyke and storm the castle. Balon capitulates and surrenders his only surviving son, Theon, as hostage and ward for his good behavior. Robert instructs Eddard Stark to take Theon under his wing.
 * 297 AL: Magister Illyrio Mopatis of Pentos invites Viserys and Daenerys Targaryen to stay in his manse and offers to help them reclaim their throne.

In the series

 * 298 AL: The events of Game of Thrones begin, seventeen years after the end of Robert's Rebellion.
 * 299 AL': By the time of the death of King Renly Baratheon, it has been eighteen years since Robert's Rebellion, indicating a year or more has passed since the events of the series began.

Differences from the books
The timeline of the books is broadly similar to the TV series, but the TV series has eliminated the reign of King Jaehaerys II Targaryen (259-261 AL), the father of the Mad King. In the series Aerys II's grandfather, Aegon V, is now his father. This was done presumably to make Aemon's explanation to Jon Snow of his familial relationships more concise.