"On s'est aimé àcause" () is a song by Canadian singer Celine Dion from her twenty-second studio album, D'elles (2007). It was written by Françoise Dorin, Marc Dupré, and Jean-François Breau, and produced by Tino Izzo. Although not released as a single, the song received significant radio airplay in Quebec in August 2007, reaching number five on the ADISQ Radio chart and number 23 on the Canadian Adult Contemporary chart. In 2018, it peaked at number three on the Quebec Digital Sales chart.
The lyrics were written by French novelist Françoise Dorin, while the music was composed by Canadian singer-songwriters Marc Dupré and Jean-François Breau. The track was produced by Canadian guitarist and producer Tino Izzo. Dion performed "On s'est aimé àcause" in May 2007 during a Canadian television special on TVA promoting the release of D'elles.
"On s'est aimé àcause" entered the BDS Radio chart on 25 August 2007, peaking at number six and remaining on the chart for 27 weeks. On the ADISQ Radio chart in Quebec, it reached number five. The song also entered Billboards Canadian Adult Contemporary chart in September 2007, where it peaked at number 23 and spent 16 weeks on the chart. Following a performance of the song on La Voix in April 2018, it debuted and peaked at number three on the ADISQ Digital Sales chart in Quebec.
D'elles also includes a reworked version of "On s'est aimé àcause", titled "A cause" (). Dorin's lyrics were adapted to suit a dance-oriented arrangement. The music was composed by Jacques Veneruso, who produced the track with Thierry Blanchard. Dion performed "A cause" in France in May 2007 during a television special on TF1 promoting the album.
"A cause" was remixed by French producer DJ Rien (Luc Bruaud). On 22 January 2008, it was announced that the remix would be promoted as the next single from D'elles in France. The promotional CD single included the album version, the radio edit remixed by DJ Rien, and "Alone" as the third track. An extended remix (3:41) was posted by DJ Rien on his Myspace page.
Dion had been expected to perform "A cause" on Star Academy on 25 January 2008. Instead, she performed "Alone" from her English-language album Taking Chances. On 7 February 2008, media outlets received a promotional envelope containing "Alone", replacing "A cause".