Hits 51 is a compilation album released in the UK in December 2001. It contains 50 tracks over two CDs, including two number one singles on the UK Singles Chart from Westlife and Bob The Builder. Bob The Builder's Mambo No. 5 appeared on Hits 50 as well in its original version by Lou Bega.Like Hits 50, a lot of the songs were edited to fit 25 tracks on one CD, but this would be the last numbered Hits album to do so. Thus, the subtitle 50 Tracks - 50 Hits! was last used on this album