"I Write Sins Not Tragedies" is a song by American rock band Panic! at the Disco, and is the second single from their debut studio album, A Fever You Can't Sweat Out (2005). It was released on April 27, 2006 on both CD and 7" vinyl. The pizzicato cello motif that the song is built upon was played by session musician Heather Stebbins. The song reached No. 7 on the United States Billboard Hot 100. This was the band's only top forty hit until the release of "Hallelujah" in 2015. While the song failed to hit the top 10 on the Alternative Songs chart peaking at No. 12 which was lower than their prior single, "The Only Difference Between Martyrdom and Suicide Is Press Coverage" which peaked at No. 5, the song's success on the Hot 100 and Mainstream Top 40 (at No. 2) charts was what made the song one of the biggest modern rock hits of 2006 and is still one of the band's most played songs on alternative radio stations to this day.

In the UK, the song was released on February 27, 2006 as a limited edition single with a free sticker. Because the sticker was included with the CD single, the song was not eligible for the UK Singles Chart. Official Charts Company rules state that stickers are not allowed in single releases. Later, in September 2006, due to the popularity of the track and following further single releases there of "Lying Is the Most Fun a Girl Can Have Without Taking Her Clothes Off" and "But It's Better If You Do", going top 40 there, the single was re-released on October 30, 2006. Despite receiving significant radio airplay upon its re-release, the single only reached No. 25 in the UK Singles Chart.

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