Panasonic G3 has a Micro Four Thirds lens mount and currently there are 108 native lenses available for this mount.
Panasonic G3 doesn't have a sensor based image stabilization system but 31 of these lenses already comes with optical image stabilization.
Since Panasonic G3 has a Four Thirds sensor, it has a focal length multiplier of 2× so you have to multiply lenses original focal length with this multiplier to find the Full Frame equivalent focal length of the lens when mounted on G3.
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Panasonic G3 Lenses with Image Stabilization
Panasonic G3 Lenses with Weather Sealings