The first cotton gin (that we know of) was invented in India some time in the 5th century AD, but archaeologist suspect that a form of cotton gin was developed and used much earlier. Eli Whitney invented the saw gin, a type of cotton gin that was able to handle short staple cotton. Earlier gins only worked well with long staple cotton. Some sources credit Catherine Littlefield Greene with giving Whitney the idea for his gin, but this seems to vary from source to source.