An air conditioner includes a plurality of compressors, a plurality of oil separators, a plurality of oil collection pipes, a common inlet pipe, and a plurality of branch inlet pipes. The oil separators are connected to outlets of the compressors for separating a refrigerant and/or oil discharged from the compressors. The oil collection pipes are respectively connected to the oil separators for collecting oil separated by the oil separators. The common inlet pipe receives the collected oil and allows the oil to flow to the compressors. The branch inlet pipes branch off from the common inlet pipe and are respectively connected to the compressors.