"Illegal" is a song recorded by Colombian singer-songwriter Shakira for her seventh studio album, Oral Fixation, Vol. 2 (2005). It was written and produced by Shakira and Lester Mendez and it features Mexican guitarist Carlos Santana. Epic Records released the song as the album's third and final single on 28 August 2006, following the release of "Hips Don't Lie". "Illegal" is a pop and country ballad with lyrics concerning mourning of a past lover complete with an understated vocal performance by Shakira and an electric guitar riff by Santana throughout. It received mixed reviews from music critics, who compared it with Alanis Morissette's material and were mixed towards Santana's contribution.

The song achieved moderate success, topping the chart in Romania and the US Dance Club Songs chart and peaking within the top ten in Austria, Italy, Netherlands, Hungary and Switzerland among other countries. The music video for the song, co-directed by Jaume de Laiguana and Shakira, had its premiere on 16 November 2006 on MTV's Total Request Live (TRL). It features the singer portraying a girlfriend of a boxer and follows a similar storyline to the song's lyrics. "Illegal" has been performed by the singer live on few occasions, such as during the MTV 5 Star event (2005) and Good Morning America (2006).