Illegal may refer to:

• Violation of law
  • Crime, an act committed in violation of criminal law
• An illegal immigrant

• The Illegal (novel) (2015), by Canadian writer Lawrence Hill
• Illegal - Justice, Out of Order, an Indian web series

• Illegal (1932 film), British
• Illegal (1955 film), American
• Illegal (2010 film), Belgian
• The Illegal (2019), film starring Suraj Sharma

• Illegal (group), a 1990s rap group
• "Illegal" (song), a track from pop singer Shakira's 2005 release, Oral Fixation Vol. 2
• Los Illegals, a music band

• All pages with titles beginning with Illegal
• Illegal agent, also known as Operational cover
• Illegals Program, Russian spies arrested in the United States in 2010
• The Illegal (disambiguation)
• Illegalism, an anarchist philosophy which openly embraced criminality as a lifestyle