An oil separator and an air conditioner including an oil separator are provided. The oil separator may include a housing including a suction tube that guides a refrigerant, in which an oil may be mixed, into the housing and a discharge tube that discharges refrigerant separated from the refrigerant, in which the oil may be mixed, to the outside, a first collection tube that communicates with a lower portion of the housing to discharge the oil separated from the oil to a compressor, a second collection tube that communicates with a side surface of the housing to discharge the oil separated from the refrigerant to the compressor, and a control valve provided in communication with the first collection tube or the second collection tube to control a flow of the oil through the first collection tube or the second collection tube.