The thinnest skin is found on your eyelids.
It's a mere 0.05 mm (two thousandth of an inch) thick there. The thickest skin? That's found on the sole of your foot. It's 4 mm (about 5/32th of an inch) thick. That's an 80-fold difference in thickness between the thinnest and the thickest skin in different parts of your body.
Source: 50 Incredible Facts About Skin