NNO

NNO may stand for:
 * Nuveen North Carolina Dividend Advantage Municipal Fund 2 (stock symbol: NNO)
 * Natural number object, in category theory, a subfield of mathematics
 * National Night Out, a crime prevention activity in the United States
 * Nynorsk, ISO 639-2 and ISO 639-3 language codes
 * Nitrous oxide