"Qué Hiciste" (English: What Did You Do?) is a song recorded by American entertainer Jennifer Lopez for her fifth studio album, Como Ama una Mujer (2007). It was written and produced by Marc Anthony and Julio Reyes Copello, with additional writing from Jimena Romero. "Qué Hiciste" became a commercial success for Lopez, appearing in a wide range of charts around the world. The song became her first Spanish-language song to chart inside the Billboard Hot 100, reaching a peak position of eighty-six. It also peaked atop of Billboard's Hot Dance Club Play and Hot Latin Tracks charts. The song additionally reached the top position in Italy and in Switzerland. Lopez performed the song on American Idol on April 11, 2007; becoming the first artist ever to perform a Spanish song on the show.

"Qué Hiciste" is a Latin rock song, with a length of four minutes and fifty-eight seconds (4:58). The song was written by Jimena Romero, Julio Reyes, Marc Anthony, and produced by Estéfano and Reyes. The song marked the beginning of a musical project that lasted for three years and was originally conceived from a dream that Anthony had with Spanish recording artist Rocío Dúrcal two weeks after the singer's death. According to him, Dúrcal asked him to listen to a piece of music, which turned out to be the primary melody for the song. He elaborated that, within the dream, Dúrcal told him that the song, yet to be titled, was exclusively "for Jennifer." Lopez revealed that as Anthony did not want to forget the lyrics, and without any studio equipment nearby, she grabbed her phone, called up her answering machine and asked her husband to sing the melody. She also revealed that, with the help of a composer, "Que Hiciste" was finished in a couple of weeks. After a few months, Lopez started to write the lyrics with a Spanish songwriter, and finished it on fifteen minutes. Lopez asserted that recording a song in her parents' language was "a dream come true" for her.

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