Sony A9 has a Sony E lens mount and currently there are 115 native lenses available for this mount.
A9 also has a sensor based image stabilization system which means that all of these lenses will be stabilized when used on A9.
Since Sony A9 has a Full frame sensor, it has a focal length multiplier of 1x so lenses will provide their original focal length on A9.
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Sony A9 Lenses with Image Stabilization
Sony A9 Lenses with Weather Sealings