"I Know Him So Well" is a duet from the concept album and subsequent musical Chess by Tim Rice, Benny Andersson and Björn Ulvaeus.

In this duet, two women – Svetlana, the Russian chess champion's estranged wife, and Florence, his mistress – express their bittersweet feelings for him and at seeing their relationships fall apart.

[3] They laid down their vocals separately and never met during the recording of the song, only for the video and subsequent performances on Top of the Pops and the European tours.

[5] In the United Kingdom on 18 September 2004, the BBC's All-Time Greatest Love Songs (hosted by Lionel Richie) saw the duet performed live by Paige and Dickson, together for the first time in 20 years, to a rapturous reception.

The song version was included in the North American leg of Houston's Moment of Truth World Tour.

"[12] Rolling Stone's Vince Alleti criticized the song and production, saying, "Walden covers all these bases, out-schlocking Masser with 'I Know Him So Well'—a genuine if frankly derivative show tune (from Tim Rice's Chess) treated here with deadly reverence..."[13] St. Petersburg Times called the duet lifting and praised the mother's role: "Mom adds a brief, welcome moment of grainy soulfulness to the album.

The song is a duet with Melanie C's fellow Spice Girls group member Emma Bunton.