"Un-Break My Heart" is a song recorded by American singer Toni Braxton for her second studio album, Secrets (1996). The song was written by Diane Warren and produced by David Foster. It was released as the second single from the album in October 21, 1996, through LaFace Records. The song is a ballad about a "blistering heartbreak" in which the singer begs a former lover to return and undo the pain he has caused. It won Best Female Pop Vocal Performance at the 39th Annual Grammy Awards in 1997. It has sold over 10 million copies worldwide nearly 3 million in the United States alone, making it one of the best selling singles of all time.

"Un-Break My Heart" attained commercial success worldwide. In the United States, the song reached number one on the Billboard Hot 100, where it stayed a total of eleven weeks, while reaching the same position on the Hot Dance Club Songs and Adult Contemporary component charts. When Billboard celebrated their 40 years charting from 1958 to 1998, the song was declared as the most successful song by a solo artist in the Billboard Hot 100 history. In Europe, the song reached the top five in more than ten countries while peaking at number one in Austria, Belgium (Wallonia), Sweden, and Switzerland.

Bille Woodruff directed the accompanying video for the single. It portrays Braxton mourning the death of her lover, while remembering the good times they had together. Braxton performed the song on the opening ceremony of the 1996 Billboard Music Awards. "Un-Break My Heart" has been covered by several artists, including American alternative rock band Weezer on the album Death to False Metal.