In this presentation I will look at the central role played in Ancient Greek identity formation by the duality Greek / Barbarian, originally constructed on linguistic grounds, but eventually evolving into other significant cultural areas. Bárbaroi was how the Ancient Greeks referred to all the foreign peoples around them whose language was not understandable. It was, of course, an onomatopoeia that allowed them to imitate the apparent stammer of those who were speaking so “strangely”. Interestingly enough the word, particularly with its passage through Latin, became to be the base of something different, to be perceived in the concept of barbaric. And so, those who could not or did not speak your language became uncivilized. People(s) not knowing the Greek language, not participating in Greek civilization, religion or literature started to be perceived not only as “different” but as somehow “inferior”. One of the legacies of Ancient Greece is then the word “barbarian”, still used today in English and many modern languages. This question has been studied extensively, as it says a lot about Greek and Roman culture in general. However, what has been not so much looked at is the extent of negativity in the attitudes towards immigrants and foreigners in Greek and Roman society. I will reflect in all these questions, and on how this is echoed in more recent times.