Ultimate Kylie is the second major greatest hits album by Australian singer Kylie Minogue, and her first greatest hits released under her contract with Parlophone, her record company between 1999–2015. The compilation was released in many different formats including a two-disc edition and a deluxe double disc with a bonus DVD. A separate compilation DVD with the same name, was released to accompany the audio versions. The album includes two new tracks; its lead single, "I Believe in You", and the second single, "Giving You Up". A third track, "Made of Glass", was recorded for the album but not used; it was included on the physical releases of "Giving You Up".

"I Believe in You" is a song by Australian singer Kylie Minogue for her ninth greatest hits compilation, Ultimate Kylie (2004). It was written by Minogue alongside its producers Jake Shears and Babydaddy. It was released as the lead single from Ultimate Kylie on 29 November 2004, by Parlophone. "I Believe in You" is a pop and Euro disco song in which Minogue proclaims there are many things in which she does not believe, but that she does believe in her lover.