Since the time of olden Rome, the city has always been a site for colonization. This once extensive to all reaches of the Roman Empire, but was more cramped to the rest of Italy in later centuries, as Rome's political power waned. Still, many of its citizens' families invent from outside the city, and the Romanesque phrase Romano de Roma has been coined to indicate someone who descends from a family that has lived in Rome for at least seven generations, the mark of a "true" Roman.

Over the next half of 20th century, Rome has seen rising immigration from other countries. There currently is an important immigrant population, including a great number of clandestine. The 2005 ISTAT estimations state that 145,000 immigrants live in the commune, or 5.69% of the total commune inhabitants. The foreign population in the metropolitan area of Rome consists in 206,000 persons, or 5.37% of the total urban area population. The foreign population in the metropolitan area of Rome is about 248,000 persons or 4.67% of the whole metropolitan area population. By far the largest number of immigrants is Eastern European, with the largest figures of foreigners coming from Romania, The Philippines, Poland, Albania, Peru, Bangladesh, and Ukraine.