Panasonic S1R has a Leica L lens mount and currently there are 65 native lenses available for this mount.
The latest released lenses that are compatible with the S1R are the Sigma 17mm F4 DG DN C, the Sigma 50mm F2 DG DN C and the Leica SL 100-400 f5-6.3.
S1R also has a sensor based image stabilization system that is up to 6.0-stops effective which means that all of these lenses will be stabilized when used on the S1R.
Since Panasonic S1R has a Full frame sensor, it has a focal length multiplier of 1x so lenses will provide their original focal length on S1R.
You may also also be interested in these:
Panasonic S1R Lenses with Image Stabilization
Panasonic S1R Lenses with Weather Sealings