Some people claim that a song by Gustav Mahler called "Ich bin der Welt abhanden gekommen," is the most beautiful ever written.

http://www.youtube.com/watch?v=pBTnAmWkxC0

That's a link to a recording of it by Janet Baker, on Youtube.

Not sure what the most "beautiful" song I've ever come across is, but this one's in the running.

A link to the song's lyrics, with translation from German to English:

http://glenngould.org/f_minor/msg04351.html

Mahler was an interesting composer. He liked to work themes and melodies from his songs into his symphonies.

What's the most beautiful song you've ever heard?