"Nobody Knows" is a song by Pink, and was the fourth single from her fourth album, I'm Not Dead (2006). It was released on November 20, 2006 in Britain and Ireland and during January 2007 in Australia and Europe. The song recorded significant digital sales in 2012 with the release of P!nk's sixth album The Truth About Love but never made a Hot 100 debut.

"Nobody Knows" was written by Pink and co-written and produced by Billy Mann. The song is a piano-ballad and deals with her feelings of depression. The song received positive reviews. IGN's wrote that "'Nobody Knows' goes for a shiny blues ballad feel, Pink flexing her vocal chords to reveal a downright sweetness to her voice." Quentin Huff from PopMatters wrote an extensive review about the song, stating that "Even when you feel like you’ve heard it before, her smoky vocals and clever touches let you know it’s not the same old thing." While commenting about her voice, he said that she "belts out her lyrics like a champ."Entertainment Weekly's Chris Willman wrote that the song can be skipped while listening to the album, while referring the track as a "stab at Xtina-style balladic solipsism, Pink's vocal span from G3 to G5"

The song was released as a single on November 20, 2006 in the United Kingdom and Ireland, and on January 13, 2007 in Australia; it reached number 27 in all three countries. It was the only physical single from I'm Not Dead to miss the top five on the ARIA Singles Chart, on which it reached its peak in late January 2007, but it was very popular on radio. Two weeks before this, "Who Knew" (the second I'm Not Dead single) had re-entered the chart and "U + Ur Hand" was still on the chart, which meant that three singles by Pink were in the top fifty (as of January 21, 2007). On the UK Singles Chart it was Pink's lowest peaking single at the time, and the first I'm Not Dead single to miss the top ten.

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