Necessary Evil may refer to:

• Necessary evil, an evil that must be allowed for a greater good to result
• Lesser of two evils principle

• The Necessary Evil, a 1925 American silent film
• Necessary Evil (2008 film), an American thriller film
• Necessary Evil: Super-Villains of DC Comics, a 2013 documentary film
• "Necessary Evil" (Star Trek: Deep Space Nine), a television episode
• "A Necessary Evil" (In the Heat of the Night), a television episode
• "A Necessary Evil" (Xena: Warrior Princess), a television episode

• Necessary Evil (Deborah Harry album) or the title song, 2007
• Necessary Evil (Salem album), 2007

• "Necessary Evil", by Armand Van Helden from 2 Future 4 U
• "Necessary Evil", by Balance of Power from Heathen Machine
• "Necessary Evil", by Body Count from Born Dead
• "Necessary Evil", by the Dresden Dolls from Yes, Virginia...
• "Necessary Evil", by Hans Zimmer from The Dark Knight Rises film soundtrack
• "Necessary Evil", by Motionless in White from Graveyard Shift
• "Necessary Evil", by Napalm Death from Enemy of the Music Business
• "Necessary Evil", by Nikki Yanofsky from Little Secret
• "Necessary Evil", by Unknown Mortal Orchestra from Multi-Love

• Necessary Evil (aircraft), a B-29 Superfortress used in the 1945 atomic bomb attack on Hiroshima
• Necessary Evil (comics), a 2019–2020 Power Rangers crossover event
• Necessary Evil, a role-playing game campaign setting by Savage Worlds
• Necessary Evil, a comic published by Desperado Publishing
• A Necessary Evil, a Stargate audiobook
• A Necessary Evil, novel by Abir Mukherjee