Lunacy may refer to:
- Lunacy, the condition suffered by a lunatic, now used only informally
- Lunacy (film), a 2005 Jan Švankmajer's film
- Lunacy (video game), a video game for Sega Saturn
- Luna Sea, a Japanese rock band originally named Lunacy
- Lunacy (album), their 2000 album
- The following of the Roman goddess Luna, a variation of the Greek goddess Selene
- Lunacy (FIRST), the name of the FIRST Robotics Competition 2009 game
- Luna-C (born 1973), British DJ and record producer