The Greek diaspora or Hellenic diaspora, also known as Omogenia refers to the communities of Greek people living outside the traditional Greek homelands, but more commonly in other parts of the world, such as the United States, Canada, Australia, the UK, Germany, Sweden, Belgium, Italy, Argentina, South Afria, Russia or other countries around the world. Members of the diaspora can be identified as those who themselves, or whose ancestors, migrated from the Greek homelands.
In modern times, in the 20th and 21st century, most Greeks left their homeland mostly for economic reasons. The largest migrations happened during the turn of the 20th century, mainly towards the United States, then after World War I when Greeks living in Asia Minor were forced to flee their homes and migrate to mainland Greece or anywhere else in the world. Big immigration spikes also happened during and after World War II, the Greek Civil War (1946-49) and the Turkish invasion of Cyprus (1974).
Today the most important centers of Greek diaspora are the New Your City, Bost and Chicago in the US, as well as London, Melbourne, Sydney, Montreal and Toronto. It's estimated that the number of Greeks living outside Greece and Cyprus are around 7 million. Around 3 million of them live in the US, 700,000 in Australia, 400,000 in the UK, 400,000 in Germany and around 300,000 in Canada. Smaller Greek communities exist in South America, mainly in Argentina, Brazil and Chile, in several other European countries (Sweden, Italy, Belgium, Switzerland, Netherlands) and other places throughout the world.
There's an old Greek saying which asserts that you'll find a Greek in the most remote place in the world, and this is not far from true. There are Greeks in such remote places as Papua, New Guinea and Madagascar. No matter where Greeks live they usually maintain a connection with the motherland, be it a connection with some family member still living back home or a "spiritual" and "cultural" connection to the land of our forefathers. There are countless stories of how strong these ties are, when oe visits remote place in the world and meets some 3th-4th generation Greek who can't even say a word in Greek yet he'll proudly say "I'm Greek! My ancestors were Greeks".
Greek citizenship is acquired by birth by all persons born in Greece, and all persons born to at least one parent who is a registered Greek citizen. People born out of wedlock to a father that is a Greek citizen and a mother that is a non-Greek automatically gain Greek citizenship if the father recognizes them as his child before they turn 18.
Nationality law of Greece is based on the principle of jus sanguinis. Greek citizenship may be acquired by descent or through naturalization. Greek law permits dual citizenship. A Greek national is a citizen of the European Union, and therefore entitled to the same rights as other EU citizens.
Any person who is ethnically Greek born outside Greece may become a Greek citizen through naturalization, providing he/she can prove a parent or grandparent was born as a national of Greece. The Greek ancestor's birth certificate and marriage certificate are required, along with the applicant's birth certificate, and the birth certificates of all generations in between until the relation between the applicant and the person with Greek citizenship is proven.