SheepShaver is an open source PowerPC Apple Macintosh emulator originally designed for BeOS and Linux. The name is a play on ShapeShifter, a Macintosh II emulator (made obsolete by Basilisk II), which is in turn not to be confused with a third-party preference pane for Mac OS X with the same name. The SheepShaver (and ShapeShifter) project was originally conceived and programmed by Christian Bauer. However, the main developer behind SheepShaver, as of late, has been Gwenolé Beauchesne.

SheepShaver was originally commercial software when first released in 1998, but after the demise of Be Inc., the maker of BeOS, it became open source in 2002. It can be run on both PowerPC and x86 systems; however, it runs more slowly on an x86 system than on a PowerPC system, due to instruction conversion.

It has also been ported to Microsoft Windows. Ports to the Mac OS X PowerPC and Intel versions have also been released. A complete install for Intel Macs can be found blank">here.

It is capable of running _Mac OS 7.5.2 through 9.0.4 (though it needs the image of an Old World ROM to run Mac OS 8.1 or below), and can be run inside a window so that the user can run classic Mac OS applications and BeOS or Linux or Windows applications at the same time.

Although SheepShaver does have Ethernet support and CD-quality sound output, SheepShaver does not emulate a memory management unit, as is the case with Basilisk II, and thus cannot run later versions of Mac OS 9 or any version of Mac OS X, which is best emulated by PearPC. At the present, SheepShaver's developers do not have plans to add MMU emulation, since it would hinder the performance of the emulator.