Amnon was a seer of Beleriand who in the First Age predicted the Fall of Gondolin by Morgoth's army. 
The name of his prophesy was Great is the Fall of Gondolin, and King Turgon himself in fact quoted this prophesy when the event actually took place in the year 510. 
- ↑ The History of Middle-earth, Vol. I: The Book of Lost Tales, chapter 7: "The Flight of the Noldoli"
- ↑ The History of Middle-earth, Vol. II: The Book of Lost Tales 2, chapter 3: "The Fall of Gondolin"