Panasonic G9 has a Micro Four Thirds lens mount and currently there are 103 native lenses available for this mount.
G9 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on G9.
Since Panasonic G9 has a Four Thirds sensor, it has a focal length multiplier of 2x 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 G9.
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Panasonic G9 Lenses with Image Stabilization
Panasonic G9 Lenses with Weather Sealings