Here's what we know:
* Ancient China: The earliest known use of nail polish was for decorative purposes. Chinese women of high status would color their nails with a mixture of beeswax, gum arabic, and dyes made from plants and minerals. They would also use gold and silver flakes to add shimmer.
* Ancient Egypt: Evidence suggests that Egyptians used henna to stain their nails and fingers. This was more of a dye than a polish.
* Mesopotamia: There is also evidence that people in Mesopotamia used henna for coloring nails as well.
It wasn't until the early 20th century that nail polish as we know it today was developed and widely used.
Therefore, while the exact origin of nail polish is unknown, the ancient Chinese are credited with the earliest known use of a true nail polish.