Events that occurred on 15 March.
 On Earth
- 1901 - Robert Havard, Inkling, is born.
- 1942 - J.R.R. Tolkien writes a letter to John Kettle.
- 1965 - Actress Robyn Malcolm is born.
- 1969 - J.R.R. Tolkien writes a letter to Amy Ronald.
- 1981 - The second episode of the 1981 radio adaptation of The Lord of the Rings is aired on BBC Radio 4.
- 2009 - Arda Reconstructed: The Creation of the Published Silmarillion is published.
 In Arda
- T.A. 2510:
- T.A. 2941:
- T.A. 3019:
- In the early morning the Witch-king breaks the Gates of Minas Tirith.
- Denethor burns himself on a pyre. Faramir is rescued by Gandalf and Beregond and brought to the Houses of Healing.
- The horns of the Rohirrim echo in the sides of Mindolluin at cockcrow.
- Battle of the Pelennor Fields:
- Frodo and Samwise escape the Tower of Cirith Ungol and begin their journey north along the Morgai.
- The Battle under the trees in Mirkwood takes place. Thranduil drives back the enemy from Dol Guldur.
- Second assault on Lothlórien.