Arwen Undómiel is a fictional character in J. R. R. Tolkien's Middle-earth legendarium. She appears in the novel The Lord of the Rings, usually published in three volumes. Arwen is one of the half-elven (Peredhil) who lived during the Third Age.

Arwen was the youngest child of Elrond and Celebrían. Her elder brothers were the twins Elladan and Elrohir. Her name, Ar-wen, means 'noble maiden'. She bore the sobriquet "Evenstar" (or Evening Star), as the most beautiful of the last generation of High Elves in Middle-earth.

As told in "The Tale of Aragorn and Arwen",^[1] Aragorn in his twentieth year met Arwen for the first time in Rivendell, where he lived under Elrond's protection. Arwen, then over 2,700 years old, had recently returned to her father's home after living with her grandmother Lady Galadriel in Lothlórien. Aragorn fell in love with Arwen at first sight. 30 years later, the two were reunited in Lórien. Arwen reciprocated Aragorn's love, and on the mound of Cerin Amroth they committed themselves to marry each other. In making that choice, Arwen gave up the Elvish immortality available to her as a daughter of Elrond and agreed to remain in Middle-earth instead of traveling to the Undying Lands.

Arwen first appears in the text of The Lord of the Rings in Rivendell, shortly after Frodo Baggins awoke in the House of Elrond: she sat beside her father at the celebratory feast. When the Fellowship of the Ring came to Lothlórien, Aragorn remembered their earlier meeting and paused in reverence on Cerin Amroth.

Shortly before Aragorn took the Paths of the Dead, he was joined by a contingent of his people, the Dúnedain of the North, accompanied by Arwen's brothers, Elladan and Elrohir, who brought him as a gift from Arwen: a banner of black cloth. The banner was unfurled at the Battle of the Pelennor Fields to reveal the emblem of Elendil figured in mithril, gems, and gold; this became the first triumphant public announcement of the King's return.

After the War of the Ring, Aragorn became king of Arnor and Gondor. Arwen arrived at Minas Tirith, and they were married. She gave Frodo the Evenstar: her necklace with a white stone, to aid him when his injuries troubled him.

Arwen is a minor character in The Lord of the Rings, but she serves as inspiration and motivation for Aragorn, who must become King of both Arnor and Gondor before Elrond would allow her to marry him.

The Tale of Aragorn and Arwen relates that Aragorn and Arwen had a son, Eldarion, and at least two unnamed daughters. In F.A. 121, one year after Aragorn's death, Arwen died at the age of 2,901 at Cerin Amroth.

Through her father, Elrond, Arwen was the granddaughter of Eärendil the Mariner (the second of the Half-elven), great-granddaughter of Tuor of Gondolin, and therefore a direct descendant of the ancient House of Hador. Through her great-grandmother, Idril, Arwen was also a descendant of King Turgon of the Noldor. Through her mother, she was the granddaughter of Lady Galadriel and the great-granddaughter of Finarfin. Éomer of Rohan said that the Lady Arwen was fairer than the Lady Galadriel of Lórien, but Gimli son of Glóin thought differently. Through both of her parents, Arwen was a direct descendant of the ancient Elven House of Finwë. Furthermore, Arwen was a descendant of Beren and Lúthien Tinúviel, whose story resembled hers. Indeed, Arwen was held to be the reappearance in likeness of her ancestor Lúthien, fairest of all the Elves, who was called Nightingale (Tinúviel).

Arwen was a very distant relative of her husband Aragorn. Aragorn's ancestor, Elros Tar-Minyatur, the first King of Númenor, was her father Elrond's brother, who chose to live as a Man rather than as one of the Eldar. Arwen eventually became Queen of the Reunited Kingdom of Arnor and Gondor when she married Aragorn, who was of the line of the Kings of Arnor. By Arwen and Aragorn's marriage, the long-sundered lines of the Half-elven were joined. Their union also served to unite and preserve the bloodlines of the Three Kings of the High Elves (Ingwë, Finwë, and the brothers Olwë and Elwë) as well as the only line with Maiarin blood through Arwen's great-great-great grandmother, Melian, Queen of Doriath, and also on Aragorn's side, through the line of kings of Arnor and Númenor to Elros, Elrond's brother, whose great-great-grandmother was also Melian.

As related in The History of Middle-earth, Tolkien conceived the character of "Elrond's daughter" late in the writing.^[2][3] Prior to this, he considered having Aragorn marry Éowyn.^[4]

Arwen does not appear in Ralph Bakshi's 1978 adaptation of The Lord of the Rings, nor in the 1980 Rankin-Bass adaptation of The Return of the King.

In Peter Jackson's The Lord of the Rings film trilogy, Arwen is played by Liv Tyler. The films gives her a more prominent role than her literary counterpart.

In the first film, Arwen searches for Aragorn and single-handedly rescues Frodo Baggins from the Black Riders at Bruinen, thwarting them with a sudden flood, summoned by an incantation. (In the novel, Elrond summons the flood, and Glorfindel takes Frodo to Rivendell.) During this flight Arwen wields the sword Hadhafang, which according to film merchandise was once wielded by her father and had belonged to his grandmother Idril Celebrindal.^[5] In the film adaptation of The Two Towers, the injured Aragorn is revived by a dream or vision of Arwen, who kisses him and asks the Valar to protect him.

Throughout the War of the Ring, Elrond begs her to accompany her kin to the Undying Lands because he does not wish to see another of his family die. Elrond shows her a vision of her sorrow-filled life after Aragorn's death, and tells her that only death awaits her in Middle-earth. Arwen reluctantly departs for Valinor. However, on the road to the Grey Havens she has a vision of her future son, Eldarion, which belies her father's one-sided prophecy. She returns to Rivendell, where Elrond admits that her mortal life will have happiness as well as grief, though he stresses that Sauron's rising power means that future is growing more and more distant. Arwen convinces her father to reforge the sword Narsil for Aragorn so that he can reclaim the throne of the King. Elrond initially refuses, but eventually agrees when Arwen begins to fall ill through her loss of immortality.

Elrond takes Narsil, reforged as Andúril, to Aragorn at Dunharrow, and tells him that Arwen's fate has become bound to the One Ring, and that she is dying. In the extended version of The Return of the King, Sauron (through a palantír) shows Aragorn a dying Arwen in order to dissuade him from battle. After Sauron's defeat, however, Aragorn reunites with Arwen at his coronation. The movies portray her as becoming human through her love for Aragorn; as in the novel, Arwen follows the choice of her ancestor Lúthien to become a mortal woman for the love of a mortal man.

The movies introduce a jeweled pendant called the Evenstar which Arwen gives to Aragorn as a token of their love. A similar pendant appears in the short story The Jewel of Arwen by Marion Zimmer Bradley, although in that story Arwen gives it to "the Ring-Bearer" rather than to Aragorn.^[6] In Tolkien's novel, Arwen gives Frodo "a white gem like a star...hanging upon a silver chain" before he leaves Minas Tirith, saying, "When the memory of the fear and the darkness troubles you...this will bring you aid".^[7] It is possible that the Evenstar was based on Frodo's jewel.

In earlier versions of the script, when the movies were supposed to be filmed in two parts under another production company, Arwen fought in the Battle of Helm's Deep and brought the sword Andúril to Aragorn. Some scenes of Arwen fighting in Helm's Deep were filmed before both the film's writers (with Liv Tyler's approval) reconsidered the change and deleted her from the sequence.^[8]

In the musical theatre adaptation of Lord of the Rings, Arwen sings the Prologue, as well as three musical numbers: "The Song of Hope", "Star of Eärendil" (with the Elven chorus) and "The Song of Hope Duet" (with Aragorn).

In the 2009 fan film The Hunt for Gollum, Arwen is played by Rita Ramnani; she appears as a vision to Aragorn after he is wounded by an orc weapon.

In the Mythopoeic Society's Tolkien on Film: Essays on Peter Jackson’s The Lord of the Rings (Mythopoeic Press, 2005), Cathy Akers-Jordan,^[9] Jane Chance,^[10] Victoria Gaydosik,^[11] and Maureen Thum^[12] all contend that the portrayal of Arwen and other women in the Jackson films is overall thematically faithful to (or compatible with) Tolkien's writings despite the differences.

John Howe's rendition of Arwen for the Lord of the Rings board game was inspired by French actress Isabelle Adjani.^[13]

The International Astronomical Union names all colles (small hills) on Saturn's moon Titan after characters in Tolkien's work.^[14] In 2012, they named a hilly area "Arwen Colles" after Arwen.^[15]