"Un-Break My Heart" is the second single from Toni Braxton's second studio album, Secrets(1996). The ballad was written by music impresario Diane Warren and produced by David Foster. The song ranked at number ten on The BillboardHot 100 All-Time Top Songs and number three on the Top BillboardHot 100 R&B/Hip-Hop Songs.

The song became Braxton's second consecutive number-one single on the Hot 100 chart. It stayed at number one for eleven weeks in a row during late 1996 and early 1997, becoming Braxton's biggest hit to date. It also rose to number two on the BillboardHot R&B/Hip-Hop Songs. Background vocals were performed by R&B singer Shanice Wilson. In the United Kingdom, the single was held off the number-one spot by the charity band Dunblane's "Knockin' on Heaven's Door"/"Throw These Guns Away", who were raising money in the light of the Dunblane massacre. After falling before peaking again at number two it was held off by the Spice Girls' "2 Become 1". In total "Un-Break My Heart" spent twelve weeks inside the UK top ten.

The music video was directed by Billie Woodruff and featured Braxton mourning the death of her lover, played by model Tyson Beckford.

Several remixes were created; one of which was Hex Hector's and Soul Solution's Club Mix, which reached number one on the Hot Dance Club Play in the first quarter of 1997.. The remix by Frankie Knuckles was also very popular in clubs in the UK and was also the version played on BBC Radio 1 and various Commercial Radio Station's A-List at the time.

The song was recorded by Braxton in Spanish as "Regresa a Mi" (translating into "Come Back to Me"). "Regresa a Mi" was first released as an additional track to the 1996 single release of "Un-Break My Heart". Il Divo (with whom Braxton would later record the duet "The Time of Our Lives") also covered this version in 2004 for their self-titled debut album Il Divo. Mexican singer Yuridia, known for her Spanish-language versions of famous English-language ballads, also included a version of the song on her album Habla El Corazón. A cover version in Russian was also recorded in 1998 by pop singer Alla Gorbacheva, called "Сердце не плачь" (transliteration: "Serdtse ne plach"; translation: "Heart, Don't Cry"). Others have covered this, including Johnny Mathis. Alexander O'Neal covered the song on his 2008 album, Alex Loves. A Hungarian version was recorded by Viktória Pintácsi, called "Széttört egy szív" ("A Heart Has Been Broken"). Filipino singer Nina also recorded her own version of the song for her 2008 album Nina Sings the Hits of Diane Warren. British band Serpentine also recorded a hard rock version.

Braxton won a Grammy Award for Best Female Pop Vocal Performance in 1997. She also won Best Female R&B Vocal Performance in the same year for the song "You're Makin' Me High".

In a 2006 poll for Channel Five's program "Britain's Favourite Break-up Songs", "Un-Break My Heart" was voted twenty-seventh.

The song also appeared as one of the official songs for the 2006 FIFA World Cup in Germany on the Voices from the FIFA World Cupalbum.