Codenamed "Arthur", the G3 name comes from the third generation of PowerPC microprocessor.

The G3 is a powerful RISC-based microprocessor, belonging to the PowerPC family of processors. It was used in Apple Macintosh computers such as the PowerBook G3, the multicolored iMacs, iBooks and several desktops, including the Power Macintosh G3s.

The G3 was introduced in two different versions, derived from the PPC 603 series of microprocessors. The PPC 740 and PPC 750 microprocessors gave x86 designers pause upon introduction. Small and extremely efficient, the PPC 740 outperformed Pentium IIs while consuming less than 20% of the amount of power and size. Derived from the PPC 740, the PPC 750 had a faster way to access L2, or backside cache, which allowed higher performance.

The earlier versions, made by Motorola, used an aluminium process for fabrication, and were limited to 400 MHz speeds. Later versions, manufactured by IBM with a "silicon-on-insulator" fabrication process, achieved speeds of 500 MHz and beyond. All G3 versions did not completely implement a standard for symmetric multiprocessing computers, which made design and manufacture of a SMP computer comparatively difficult. The G4 corrected this deficiency.

With its combination of small size and low power requirements, the G3 proved an ideal laptop microprocessor in its era. Apple ceased using the G3 on the 22nd of October, 2003.

G3 is also the generic name given to a live music show tour, prodominantly featuring instrumental guitarists, i.e. Steve Vai, Joe Satriani, Eric Johnson, Yngwie Malmsteen and Billy Sheehan, among many others.
The G3 is also an assault rifle built by the German arms manufacturer Heckler und Koch