0K (zero K) or 0-K may refer to:
- 0k, an abbreviation for zero killed (used by bombers during WWII)
- 0K, an abbreviation for the temperature zero Kelvin, or Absolute zero
- 0K, an abbreviation for Zero knowledge in cryptology
- Zero-knowledge proof
- Non-interactive zero-knowledge proof
- Zero-knowledge password proof
- Zero-knowledge proof
- 0K, an abbreviation for zero keel, a type of Suspension keel
- Zero-K, an open source real time strategy game