The Last Alliance of Elves and Men is an episode in J.R.R. Tolkien's fictional universe of Middle-earth. It was formed in 3430 of the Second Age (S.A.) in response to the threat of conquest by the Dark Lord Sauron.

Sauron had been contending with the Elves for mastery of Middle-earth for over 1200 years. Fearing the establishment of the powerful kingdoms in exile — Arnor and Gondor — by his hated enemies, the Dúnedain, Sauron launched a preemptive attack on Gondor in S.A. 3429.

In response, Elendil High King of the Dúnedain, formed an alliance with Gil-galad, the High King of the Eldar to repel Sauron's assault.

The two kingdoms assembled their armies in Arnor and marched on Sauron's forces. In S.A. 3434 they defeated Sauron's army in the Battle of Dagorlad, breeched the Morannon into Mordor, and besieged the Dark Lord's fortress of Barad-dûr. The siege lasted for seven years during which Anárion was slain, it culminated in Sauron directly engaging in the battle at which time both Elendil and Gil-galad both perished.

Sauron was finally defeated by Isildur, Elendil's eldest son, by using the broken remnant of Narsil, Elendil's sword, to cut the One Ring from Sauron's hand. Bereft of the power of the One Ring, Sauron's spirit dissipated and would not take form again in Middle-earth for a thousand years.

With the victory over Sauron, the Last Alliance was dissolved.