9O

9O or 9-O may refer to:


 * 9O, IATA code for National Airways Cameroon
 * 9°, an abbreviation for ninth in some languages
 * Grêmio Atlético do 9° Regimento; see Grêmio Atlético Farroupilha
 * 9O–9T, the ITU prefix codes for Democratic Republic of the Congo
 * 9O, squadron code for No. 44 Maintenance Unit; see List of RAF Squadron Codes