"Come away! Let the cowards keep this city!"
- Feanor rallying the Noldor to return to Middle-earth.
The Rebellion of the Noldor, also known as the Flight of the Noldor was a historic event during the Elder Days. It was when Feanor and his sons rebelled against the Valar and the other Elvish kindreds, swearing an oath to reclaim Feanor's Silmarils, which had been stolen by the Dark Lord Morgoth.
Melkor had been set free after thousands of years by the Valar, and at first it seemed that he had forgotten his plans for domination. However, he started to weave deceit through the Noldor, and soon many of the Elves in Valinor were speaking against the Valar, the most promiment of them all being Prince Feanor, son of High King Finwe.
After the Two Trees were destroyed by Melkor, the Valar asked Feanor to retrieve the Silmarils from his father's home at Formenos, so that the gems could be used to revive the light of the Trees once more. Feanor refused to do so, and was banished to Formenos for his defiance. Feanor arrived, only to find that Finwe was dead, Formenos was in ruins and the Silmarils were gone. This was the breaking point for Feanor.
Feanor came to the Valar and named Melkor Morgoth for the first time, cursing his name and his doings. He went on to tell the Elves that Morgoth was one of the Valar, and that the Valar probably knew that Morgoth would do such a thing. Through his charisma and the deceit of Morgoth, many of the Noldor started to agree. Despite the warnings of the Valar, Feanor and his 7 Sons swore a cursed oath, telling that the Sons would kill Elf, Man, Beast or Valar if it meant that they could retrieve the Silmarils once more. Fingolfin spoke against the Rebellion, but he was threatened at sword-point by Feanor within Fingolfin's halls.
Eventually, through his wish to bond with Feanor, Fingolfin and his House joined the Rebellion. The House of Finarfin also went, and soon Valinor was almost completely empty of the Noldor. The Noldor marched north, arriving at the Teleri havens of Alqualonde. The Noldor commanded the Teleri to give their ships to Feanor so that he could sail to Middle-earth. When they refused, Feanor and his Sons attacked, and the first Kinslaying began. The House of Fingolfin joined, thinking that the Teleri had swung their swords first, and soon most of the Teleri were murdered in cold-blood. However, Feanor and his House then abandoned Fingolfin after sailing away with the ships, leaving his two half-brothers to reach Middle-earth via the only other route: Helcaraxe.
Before reaching Helcaraxe, the Houses of Finarfin and Fingolfin were greeted by one of the messengers of the Vala Mandos. The messenger told the Noldor that if they should cross into Middle-earth, then they would be abandoned by the Valar for eternity. While the House of Fingolfin pressed on, Finarfin and many of the members of his House turned back, feeling guilty for their actions at Alqualonde. They were pardoned by the Valar, and Finarfin became the King of the Noldor in Valinor. Fingolfin and Feanor remained in Middle-earth, and the Rebellion finished, thus beginning the War of the Jewels.