War is a long series of battles usually happening over territorial disputes.
In all the legendarium of Tolkien's Middle-earth, war may refer to:
- First War, a conflict between Melkor and the Valar; the first ever war in Arda.
- War for Sake of the Elves, a war to overthrow Melkor and rid Middle-earth of his influence during the Years of the Trees.
- The War of the Great Jewels, a long war that started when Melkor stole the Silmarils and killed Finwë.
- The Kinslaying at Alqualondë, which Feanor and the Noldor initiated to obtain the ships they needed to get to middle Earth and fight Melkor in the War of the Great Jewels.
- For other kinslayings in the War of the Great Jewels, see Kinslaying (disambiguation)
- War of the Elves and Sauron, a war initiated by Sauron in the mid-Second Age when the Elves discovered who he was and that they had been deceived.
- War of the Last Alliance of Elves and Men, a war between the Elves and Dúnedain of Middle-earth and Sauron.
- First Easterling War, a series invasions, battles, and events that marked the beginning of Gondor's troubles with the Easterlings alone.
- Second Easterling War was a war between Gondor and the Easterlings in the mid-Third Age.
- Wainrider War was a war between the Easterling Wainriders and their allies and Gondor, and its Northmen allies.
- Angmar War, a war between Arnor and the evil realm of Angmar during the mid-Third Age.
- The Kin-strife, a civil-war in Gondor that started when the Dúnedain of Gondor refused to accept the mixed-blooded Eldacar as King of the Realm.
- War of the Dwarves and Orcs, a war started by the orcs of the Misty Mountains after they killed Thrór in Moria.
- War of the Ring, a war that was initiated by Sauron, who had gained strength since the end of the Second Age and sought the One Ring. Its end was also the start of the Fourth Age.
- Dagor Dagorath, the final battle in which the world ends and will be recreated. Melkor will rise again only to be defeated by the Valar. This is prophesied to be the final great war in Arda.