Dubbed Mountain Lion, the new system has features borrowed from the iPhone and a tighter integration with online file storage.
Apple Inc. previously disclosed the features. It announced the availability date on Tuesday as it released its earnings report for the April-June quarter.
The new system will cost $20 and will be available only for download. Only computers running the two most recent versions of Mac OS, Lion and Snow Leopard, can be upgraded.
Macs bought on or after June 11 can be upgraded for free.