Ring 0 or zero ring or variation, may refer to:

• Ring 0: Birthday, a Japanese horror prequel film
  • The Ring Volume 0: Birthday, a subsequent manga

• Ring 0 (computer security), the highest privilege level
• Telephone dialling instructions to access a switchboard operator

• Zero ring, the trivial ring in mathematics ring theory
• O̊, the letter "O" with a ring diacritical mark

• Birthday (short story collection), a Japanese anthology containing prequels and sequels to Ring
• Ring road (disambiguation)
• Ring (disambiguation)