One of Titanic's emblematic elements is undoubtedly its theme song: "My Heart Will Go On", performed by Celine Dion and later sung by millions of fans around the world. Dion, who had previously worked on the theme songs for Disney's Beauty and the Beast and Sleepless in Seattle, was afraid that her career would be pigeonholed into movie soundtracks or romantic songs, so she turned down the offer. However, after much insistence from Horner and her own husband and manager, René Angélil, Dion finally agreed, and at the first studio test, she recorded the rendition that would eventually make it into the film.

Source: Movie Web