Lúthien

Lúthien Tinúviel is an Elf, the fairest of all the Children of Ilúvatar. She is supposed to have been based on Edith Tolkien.

Lúthien was the daughter of Elu Thingol, king of Doriath, and his queen, Melian the Maia. (Technically, this makes Lúthien Half-elven, but she is counted among the Elves; the term "Half-elven" was reserved for those with human descent). Lúthien's romance with the Beren is one of the great stories of the Elder Days, and is mirrored by the later romance between Aragorn and Arwen Evenstar. Lúthien means "Enchantress" and Tinúviel means "Nightingale". Tinúviel was a name given to her by Beren (it was also the name Tolkien originally gave her, before changing it to Lúthien). She is described as the Morning Star of the Elves, while Arwen is called Evenstar, the Evening Star.

Lúthien is remembered in the Lay of Leithian. She fell in love with Beren, a Man of the House of Bëor. Their relationship was unlikely from the beginning: Lúthien was not only the cherished single daughter of the most powerful elven king in Beleriand, but also the daughter of a Maia, a powerful angelic being. Beren was a mortal man on the run from the Dark Lord Morgoth.

Thingol was desperate not to let Beren marry his daughter, and set an impossible task as the bride price: Beren had to bring to Thingol one of the Silmarils from Morgoth's iron crown. Against monstrous odds, including kidnap by the sons of Fëanor and the death of Finrod Felagund, as well as a confrontation with Sauron, the couple achieve the task, with help from Huan the Hound of Valinor, but Beren dies as soon as it is completed. In grief, Lúthien laid down and died after this event, going to the Halls of Mandos. Here, she manages to convince Mandos to grant herself and Beren life again, on the condition that they would both be mortal and die the death of Men. This was the only time when Mandos was ever moved to pity.

After this, they dwell in Ossiriand until after the sack of Menegroth. They have a son, Dior, who is called Elúchil - the Heir of Thingol. After the Silmaril stolen by Beren was set in the Nauglamír, the Necklace of the Dwarves, it was given to Lúthien. Her beauty combined with the splendor of the gem and necklace to make her home of Tol Galen the fairest land ever to have existed east of Valinor. On her death the Nauglamír was delivered to her son Dior, which leads to the ruin of Doriath.

According to legend, her line will never be broken.

On Edith's grave
Edith Tolkien was buried in Wolvercote Cemetery (North Oxford) and this name appears on her plaque:

EDITH MARY TOLKIEN LUTHIEN 1889 – 1971

The name of Beren also appears on J.R.R. Tolkien's plaque:

JOHN RONALD REUEL TOLKIEN BEREN 1892 – 1973

Earlier versions
In the various versions of The Tale of Tinúviel, Tolkien's earliest form of his tale, as published in The Book of Lost Tales Parts 1 and 2, her original name is Tinúviel (Lúthien was invented later), Beren is an Elf, and Sauron has not yet emerged. In his place, they face Tevildo, the Prince of Cats, a monstrous giant cat.

Inspirations
As said above, Tolkien considered his wife his Lúthien. The name may be derived from the Old English word Lufien, which means love.