According to the appendices of The Return of the King, Aragorn, named after his ancestor Aragorn I, was born on March 1 in 2931 of the Third Age, the son of Arathorn II and his wife Gilraen. Through his ancestor Elendil (whom he closely resembled)] Aragorn was a descendant of Elros Tar-Minyatur, Master Elrond's Half-elven twin brother and the first king of Númenor. Aragorn is descended from both of Elendil's sons, from Isildur through Arvedui, last King of Arthedain, and from Anárion through Arvedui's wife Fíriel.
When Aragorn was only two years old, his father was killed while pursuing Orcs. Aragorn was afterwards fostered in Rivendell by Elrond. At the request of his mother, his lineage was kept secret, as she feared he would be killed like his father and grandfather if his true identity as the descendant of Elendil and Heir of Isildur became known. Aragorn was renamed Estel and was not told about his heritage until he came of age in 2951.
Elrond revealed to "Estel" (hope in Sindarin) his true name and ancestry when he came of age, and delivered to him the shards of Elendil's sword, Narsil, and the Ring of Barahir. He withheld the Sceptre of Annúminas from him until he "came of the right" to possess it. It was also around this time that Aragorn met and fell in love with Arwen, Elrond's daughter, who had newly returned from her mother's homeland of Lórien.
Aragorn thereafter assumed his proper role as the sixteenth Chieftain of the Dúnedain, the Rangers of the North, and went into the wild, where lived the remnants of his people, whose kingdom had been destroyed through civil and regional wars centuries before.
Aragorn met Gandalf the Grey in 2956, and they became close friends. At Gandalf's advice he and his followers began to guard a small land known as the Shire, inhabited by the diminutive and agrarian Hobbits, and he became known among the peoples just outside the Shire's borders as Strider.
From 2957 to 2980, Aragorn undertook great journeys, serving in the armies of King Thengel of Rohan (King Théoden's father), and Steward Ecthelion II of Gondor (father of Denethor). Many of his tasks helped to raise morale in the West and counter the growing threat of Sauron and his allies, and he acquired invaluable experience which he would later put to use in the War of the Ring. Aragorn served his lords in disguise and his name in Gondor and Rohan during that time was Thorongil (Eagle of the Star). With a small Gondorian squadron of ships, he led an assault on the long-standing rebel province of Umbar in 2980, burning many of the Corsairs' ships and personally slaying their lord during the battle on the Havens. After the victory at Umbar, "Thorongil" left the field and to the dismay of his men, went East.
Later in 2980, he visited Lórien, and there once again met Arwen. He gave her the heirloom of his House, the Ring of Barahir, and, on the hill of Cerin Amroth, Arwen pledged her hand to him in marriage, renouncing her Elvish lineage and accepting the Gift of Men: death.
Elrond withheld from Aragorn permission to marry his daughter until such time as his foster son should be king of both Gondor and Arnor. To Elrond's as well as Aragorn's knowledge, in order to marry a mortal his daughter would be required to choose mortality, and thus deprive the deathless Elrond of his daughter while the world lasted. Elrond was also concerned for Arwen's own happiness, fearing that in the end she might find death (her own and that of her beloved) too difficult to bear.
Before the events of The Lord of the Rings proper take place, Aragorn also travelled through the Dwarven mines of Moria, and to Harad, where (in his own words) "the stars are strange". Tolkien does not specify when these travels occurred.
In 3009, Gandalf grew suspicious of the ring belonging to the Hobbit Bilbo Baggins, which later turned out to be the One Ring, the core of the Dark Lord Sauron's evil power. Aragorn went at his request into Rhovanion in search of Gollum, who had once possessed the Ring. He caught the creature in the Dead Marshes near Mordor, and brought him as a captive to Thranduil's halls in Mirkwood, where Gandalf questioned him.
The Lord of the Rings
In The Fellowship of the Ring, Aragorn joined Frodo Baggins, Bilbo's adopted heir, and three of his friends at the Inn of the Prancing Pony in Bree. These four had set out from the Shire to bring the One Ring to Rivendell. Aragorn, going by the nickname Strider, was aged 87 at that time, nearing the prime of life for one of royal Númenórean descent. With Aragorn's help the Hobbits escaped the pursuing Nazgûl and reached Rivendell. There, Aragorn was chosen to join the Fellowship of the Ring that was formed to guard Frodo, who was charged with destroying the Ring in the fires of Mount Doom in Mordor. Besides Aragorn, Gandalf, and Frodo, the company included Frodo's cousins Pippin and Merry, Frodo's faithful gardener Samwise Gamgee, Legolas the Elf, Gimli the Dwarf, and Boromir of Gondor. Before the group set out, the shards of Narsil were reforged, and the restored blade was named Andúril.
Aragorn accompanied the group through an attempt to cross the pass of Caradhras and through the mines of Moria. He became their leader after Gandalf was lost in battle with a Balrog. Aragorn led the company to Lórien and then down the river Anduin to the Falls of Rauros. Originally he had planned to go to Gondor and aid its people in the war, but after the loss of Gandalf he became responsible for Frodo. Frodo, however, decided to continue his quest alone (accompanied now only by Sam), and Boromir was slain by the orcs while protecting Merry and Pippin. So Aragorn, together with Legolas and Gimli, went to Rohan to free Merry and Pippin, who had been captured by the wizard Saruman's Uruk-hai.
In The Two Towers, Aragorn, Legolas, and Gimli encountered Éomer, who had recently been pursuing rumours of an Orc raid in the area. From Éomer, Aragorn learned that the Orcs who had kidnapped Merry and Pippin had been destroyed and that the Hobbits had not been found. Dejected, he led Legolas and Gimli to the site of the battle. Clues led Aragorn to believe that the Hobbits might still be alive, and he led the party into Fangorn forest. They did not find the Hobbits, but they did find Gandalf the White, sent back to continue his struggle against Sauron. Gandalf told them that the Hobbits were safe with the Ents of Fangorn. Together, the four travelled to Edoras, where Gandalf freed Théoden from Saruman's enchantment and helped him muster the Rohirrim against Saruman.
Aragorn, Legolas and Gimli then helped the people of Rohan in the Battle of the Hornburg, in which they conclusively defeated Saruman's army. In order to distract Sauron's attention from Frodo, who was approaching Mordor, Aragorn used a palantír and revealed himself as the heir of Isildur to Sauron. Sauron probably believed that the One Ring had come into Aragorn's hands; therefore he made his assault on Minas Tirith prematurely and without adequate preparation.
In order to defend the city, Aragorn entered the Paths of the Dead, and summoned the Dead Men of Dunharrow who owed allegiance to the king of Gondor. It had been prophesied by Isildur and Malbeth the Seer that the Dead would be summoned once more to pay their debt for betraying Gondor millennia before. With their aid the Corsairs of Umbar were defeated. Aragorn, a small force of Rangers, and a large contingent of men and soldiers from the southern regions then sailed up the Anduin to Minas Tirith. When they arrived at the Battle of the Pelennor Fields, Aragorn unfurled a standard that Arwen had made for him which showed both the White Tree of Gondor along with the jewelled crown and seven stars of the House of Elendil. With the help of the southern forces the armies of Gondor and Rohan rallied and defeated Sauron's army.
The restoration of the line of Elendil to the throne of Gondor is a subplot of The Lord of the Rings; Aragorn's adventures not only aid Frodo in his Quest, but also bring him closer to his own kingship — which, though his by right and lineage, has been left open for centuries due to historical, legal, and military circumstances. The people of Gondor have been under the rule of the Stewards of Gondor for centuries, as it was widely doubted that any of the royal line still lived. Shortly after Isildur's departure, Meneldil, son of Anárion, had severed Gondor from Arnor politically, although the formal title of High King remained with the northern line (as Isildur was Elendil's eldest son). This arrangement had been reinforced by the Steward Pelendur about 1,200 years before when he rejected Arvedui's claim to the Throne of Gondor during a Gondorian succession crisis (Eärnil, a member of the House of Anárion, was eventually chosen as King instead). It is worth noting, however, that Arvedui had also based his claim on the fact that he had married a descendant of Anárion: thus, Aragorn was technically a descendant of not only Elendil and Isildur but of Elendil's other younger son and Isildur's brother, Anárion.
In The Return of the King, the Steward Denethor declared that he would not bow to a descendant of Isildur (years before, he had seen "Thorongil" as a rival to his father's favour). Aragorn healed Faramir, Denethor's heir, who had been expected to die; this won him immediate recognition by Faramir as the rightful heir to the throne, and his humility and self sacrifice gained him the hearts of the inhabitants of Gondor's capital city (Aragorn's healing abilities, however, were a sign to the people of Gondor of the identity of their true king; as Ioreth said, "The hands of the King are the hands of a healer, and so shall the rightful king be known"). The people hailed him as King that same evening.
Despite his immediate success and popularity, however, and despite his claim to the throne through raising the royal banner, Aragorn decided to lay aside his claim for the time being. He knew that if he aggressively promoted his claim, rival claimants or debates as to his legitimacy were not out of the question, and this could be a fatal distraction for Gondor at a time when the West needed to be united against Sauron. So, to avoid conflict, after he had healed people during the night of March 15/16, he left Minas Tirith and symbolically refused to enter it again until he was crowned King on May 1.
In order to ensure safe passage across Mordor for Frodo to fulfil his quest, Aragorn then led the Army of the West out from Minas Tirith to make a diversionary feint on the Black Gate of Mordor itself in the Battle of the Morannon. Gandalf had been given supreme command of the war effort after the Pelennor Fields, and acted as chief spokesman in the parley with the Mouth of Sauron; but Aragorn commanded the allied troops during the battle and its aftermath.
Upon Sauron's defeat, Aragorn was crowned as King Elessar (translated as Elfstone in Tolkien's invented language of Quenya), a name given to him by Galadriel. (In Sindarin, another of Tolkien's languages, this becomes Edhelharn.) He became the twenty-sixth King of Arnor, thirty-fifth King of Gondor and the first High King of the Reunited Kingdom, though it would be several years before his authority was firmly reestablished in Arnor. His line was referred to as the House of Telcontar (Telcontar being Quenya for "Strider" which was the name he was known by at Bree and the name which he was introduced with to the hobbits). Aragorn married Arwen shortly afterwards, and ruled the Kingdom of Gondor and Arnor until 120 of the Fourth Age. His reign was marked by great harmony and prosperity within Gondor and Arnor, and by a great renewal of cooperation and communication between Men, Elves, and Dwarves, fostered by his vigorous rebuilding campaign following the war. Aragorn led the forces of the Reunited Kingdom on military campaigns against some Easterlings and Haradrim, re-establishing rule over much territory that Gondor had lost in previous centuries. He died at the age of 210, after 120 years as king. He was succeeded on the throne by his son, Eldarion. Arwen, gravely saddened by the loss of her husband, gave up her now mortal life shortly afterwards. Her grave is in Lothlórien. Arwen and Aragorn also had at least two unnamed daughters.