CNO is a three-letter initialism. It can mean:
- Carrier-to-noise ratio, abbreviated CNO in the context of the GPS
- Casualty Notification Officer
- Chief of Naval Operations
- Chief Networking Officer
- Chief nuclear officer
- Chief Nursing Officer
- Chino Airport IATA symbol: CNO
- Cis-Neptunian object
- CNO cycle - a special stellar nuclear fusion process
- .com .net .org
- Computer network operations
- Conseco, under the New York Stock Exchange ticker symbol system
CNO may also refer to:
- The chemical formula for a fulminate ion