In the works of J. R. R. Tolkien, the Noldor (also spelled Ñoldor, meaning those with knowledge in his constructed language Quenya) are a kindred of Elves who migrate west to the blessed realm of Valinor from the continent of Middle-earth, splitting from other groups of Elves as they went. They then settle in the coastal region of Eldamar. The Dark Lord Morgoth murders their first leader, Finwë. The majority of the Noldor, led by Finwë's eldest son Fëanor, then return to Beleriand in the northwest of Middle-earth. This makes them the only group to return and then play a major role in Middle-earth's history; much of The Silmarillion is about their actions. They are the second clan of the Elves in both order and size, the other clans being the Vanyar and the Teleri.

Among Elves, the Noldor show the greatest talents for intellectual pursuits, technical skills and physical strength, yet are prone to unchecked ambition and pride in their ability to create. Scholars such as Tom Shippey have commented that these attributes lead to their decline and fall, especially through Fëanor who creates and covets the magical jewels, the Silmarils. Others including Dimitra Fimi have linked the Noldor to the mythical Irish warriors and sorcerers, the Tuatha Dé Danann.

"Noldor" or "Ñoldor" means those who have great knowledge and understanding. The Noldor are called Golodhrim or Gódhellim in Sindarin, and Goldui by another kindred of Elves, the Teleri of Tol Eressëa. The singular form of the Quenya noun is Noldo and the adjective is Noldorin, which is also the name of their dialect of Quenya.

In early drafts of his legendarium, Tolkien used the name "Gnomes" for the group later called the Noldor, and their language, the Noldorin dialect of Sindarin, was called "Gnomish" or "Noldorin". Tolkien had chosen "gnome" thinking that it derived from the Greek γνῶσις, gnōsis (knowledge), and hence was a good name for the wisest of the elves. However, because of its common association with garden gnomes, Tolkien abandoned the term.

The Noldor are counted among the Calaquendi ("Elves of the Light") or High Elves, as they had seen the light of the Two Trees of Valinor. The most distinctive aspect of Noldorin culture is their fondness for craftwork and skill of their workmanship, which ranges from lapidary to embroidery to the craft of language. Among the Elven kindreds, the Noldor are the most beloved by the Vala Aulë, who originally taught them craftsmanship. As a result of their renown as the most skilled of all peoples in lore, warfare and crafts, the Noldor are sometimes called the "Deep Elves". Following their return to Middle-earth at the end of the First Age, the Noldor build great cities within their realms in the land of Beleriand, such as Nargothrond and Gondolin.

When the Noldor are in Valinor they speak Quenya; in Middle-earth they also speak Sindarin. Among the wisest of the Noldor is Rúmil, creator of the first writing system, Sarati, and author of many books of lore. Fëanor, son of Finwë and Míriel, is the greatest of their craftsmen, "mightiest in skill of word and of hand", and creator of the Silmarils. Fëanor also devised the Tengwar script.

Tolkien gave some Noldorin leaders like Finwë and Fingolfin their own heraldic devices, carefully distinguishing their ranks by the number of points touching the rim.

The Noldor are the proudest of the Elves, as they vaunt in particular their ability to create: in the words of the Sindar, "they needed room to quarrel in". Equally, this causes in them an arrogance that plagues their history and causes them great suffering.