Panasonic S1 has a Leica L lens mount and currently there are 66 native lenses available for this mount.
The latest released lenses that are compatible with the S1 are the Sigma 14mm F1.4 DG DN, the Sigma 17mm F4 DG DN C and the Sigma 50mm F2 DG DN C.
S1 also has a sensor based image stabilization system that is up to 6.5-stops effective which means that all of these lenses will be stabilized when used on the S1.
Since Panasonic S1 has a Full frame sensor, it has a focal length multiplier of 1x so lenses will provide their original focal length on S1.
You may also also be interested in these:
Panasonic S1 Lenses with Image Stabilization
Panasonic S1 Lenses with Weather Sealings