"Who's That Girl" is a song by American singer Madonna from the soundtrack of the 1987 film Who's That Girl.
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. In 2009, it was included on Madonna's third greatest hits compilation, Celebration.
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 film 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".
Upon release, the song received positive to mixed reviews from music critics; the similarities to "La Isla Bonita" were both praised and criticized. "Who's That Girl" became Madonna's sixth single to top the Billboard Hot 100, which made her the artist with the most number one hits in the 1980s decade.
It was also successful overseas: it reached the top of the charts in the United Kingdom, the Netherlands, Italy, Ireland, and Belgium. The song was nominated for Best Song Written for Visual Media at the 1988 Grammy Awards, and for Best Original Song at the 45th Golden Globe Awards.
The accompanying music video mixed together footage from Who's That Girl and scenes of Madonna wandering around a park, decked out in a Latin-inspired outfit.
The track was included on the singer's Who's That Girl (1987) and Rebel Heart (2015 - 2016) concert tours, and has been covered by some artists, particularly for tribute albums.