"Who's That Girl" is a song by American singer Madonna from the soundtrack of the 1987 film of the same name. Written and produced by Madonna and Patrick Leonard, it was released in Europe as the soundtrack's lead single on June 29, 1987; in the United States, a release was issued the following day. An uptempo pop song, "Who's That Girl" continued the singer's fascination with Latin pop, a genre she had previously explored on her single "La Isla Bonita". It features instrumentation from drums, bass, and trumpets, and has lyrics sung both in English and Spanish. While shooting for the film, then called Slammer, Madonna had requested Leonard to develop a song that captured the nature of her character; the producer worked on a demo and, afterwards, Madonna added the lyrics and decided to rename the song, as well as the film, to "Who's That Girl".

Who's That Girl is the first soundtrack album by American singer and songwriter Madonna. It was released on July 21, 1987, by Sire Records to promote the film of the same name. It also contains songs by her label mates Scritti Politti, Duncan Faure, Club Nouveau, Coati Mundi and Michael Davidson. The soundtrack is credited as a Madonna album, despite her only performing four of the nine tracks on the album. After the commercial success of the film Desperately Seeking Susan (1985), in which she co-starred, Madonna wanted to act in another comedy film titled Slammer, about a woman named Nikki Finn who was falsely accused of homicide. However, due to the critical and commercial failure of her adventure film Shanghai Surprise (1986), Warner Bros. was initially reluctant to greenlight the project but later agreed.