It is not known who first invented scissors, because they have been around for so long. Scissors of a simple kind existed in ancient Egypt at least 1500 years ago, and similar tools have been found in the remains of even earlier cultures. The scissors used in older cultures were often made of a single thin piece of metal bent into a U shape and sharpened at the ends; you would squeeze the ends together and they would spring apart when you released them after use.
Scissors more like the ones that we know today, made of two pieces of crossed metal sharpened all down the sides to form blades, appeared in ancient Rome about 100 AD, though they looked more like shears. These tools were usually made of iron.
By 600 you can find evidence of the use of modern scissors, with the two blades held together by a pivot. These may well have been developed earlier by the Romans, but it's not known for sure.