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
See also 9° O9 (disambiguation) 90