What is the highest note ever sung by a human being?

Somewhere around F, over 3 octaves above Middle C. I don't know who produced the note. That would be somewhere in the area of 2,800 Hertz.

Yma Sumac could sing C in alt - the C above high C. F is probably the highest note ever written - eg Mozart's the impressario and Queen of the Night in Zauberflote.

As a die-hard fan of Mme. Sumac, a gorgeously exotic oasis amid the Pat Boone-Connie Francis deserts of the 50's, may I beg to edit Mibs' answer from could to can, and still does. Long may she trill.

The note I was talking about was an octave higher than Mozat's Queen of the Night could sing.

In March 1770 Leopold Mozart (Amadeus’s father) heard the soprano Lucrezia Aguiari (also spelled Agujari) hit C in altissimo; that’s three octaves above middle C, but admittedly a fourth below Arpeggionist’s record.

It is generally agreed that standard concert pitch has been forced up a semitone or so since Mozart’s day, so a modern ear with perfect pitch would hear the note as B (five ledger lines above the stave).

Julie Andrews was said to have a range of 5 octaves. If this is true, and her range started one octave below Middle C (as is the case for most women, especially singers), then she could have even topped the record I know of (which is really more of a scream than a sung note usually).

Georgia Brown of Brazil holds the Guinness World Record for this, I believe the note was G10, that is to say, six and a half octaves above middle C. Whether this could be described as singing is debatable, but is certainly the highest pitch produced by a human voice on record.

Georgia Brown is a Brazilian singer noted for her extensive vocal range. She currently holds the Guinness World Records for hitting the highest vocal note and for possessing the greatest range, which spans exactly 8 octaves from G2-G10 using scientific pitch notation. She also has 5 octave of singing voice.

https://en.wikipedia.org/wiki/Georgia_Brown_(Brazilian_singer)

Julie Andrews hit F above top C at the age of 12.
You can hear it here at the end:
http://uk.youtube.com/watch?v=iV2-YGGn0y4