"For I am the daughter of Elrond. I shall not go with him when he departs to the Havens: for mine is the choice of Lúthien, and as she so have I chosen, both the sweet and the bitter."

I would rather share one lifetime with you than face all the Ages of this world alone.
—Arwen to Aragorn

Arwen was the Half-Elven daughter of Elrond and Celebrían. She was often called Arwen Undómiel or "Evenstar".

In marrying Aragorn II Elessar after the War of the Ring, she became Queen of the Reunited Kingdom of Arnor and Condor, and like Beren and Lúthien before her, she united Elf and Man in peaceful love and harmony, in the process becoming mortal. Arwen arrived at Minas Tirith after Aragorn had become King of Condor and Arnor, and they married on Midsummer's Day in the year TA 3019, after the end of the War of the Ring. She became Queen of the Reunited Kingdoms of Arnor and Gondor. After marrying Aragorn, she bestowed upon Frodo Baggins a gift; her place on the ships to Valinor. She bore Aragorn's son, Eldarion, and several daughters.

Arwen was the youngest child of Elrond and Celebrían; her elder brothers were the twins Elladan and Elrohir. Through her father, she 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. Arwen was also a descendant of King Turgon of the Ñoldor through her great-grandmother, Idril. Through her mother, she was the granddaughter of the Lady Galadriel and the great-granddaughter of Finarfin. Éomer of Rohan said that the Lady Arwen was more fair 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 ancestress 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 one of the Eldar. This means that Aragorn also has very distant Elvish ancestry. Elros died in SA 442, some 3240 years before Arwen was born.  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.  After the War of the Ring ended, Arwen and Aragorn produced the future heir of the throne, Eldarion.

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.