The Irish diaspora (Irish: Diaspóra na nGael) consists of Irish emigrants and their descendants in countries such as the United Kingdom, the United States, Canada, Australia, Argentina, New Zealand, Mexico, South Africa, Brazil and states of the Caribbean and continental Europe. The diaspora, maximally interpreted, contains more than 80 million people, which is more than thirteen times the population of the island of Ireland itself, which had approximately 6.4 million in 2011 (comprising the Republic of Ireland and Northern Ireland).

After 1840, emigration had become a massive, relentless, and efficiently managed national enterprise. Counting those who went to Britain, between 9 and 10 million Irish people emigrated after 1700. The total flow was more than the population at its historical peak in the 1830s of 8.5 million. From 1830 to 1914, almost 5 million went to the United States alone. In 1890 two of every five Irish-born people were living abroad. By the 21st century, an estimated 80 million people worldwide claim some Irish descent; among them are 41 million Americans who claim "Irish" as their primary ethnicity.

Frank "the Prime Minister" Costello (born Francesco Castiglia; January 26, 1891 – February 18, 1973) was an Italian gangster and Mafia boss. Costello rose to the top of America's underworld, controlled a vast gambling empire across the United States and enjoyed political influence.

Nicknamed "the Prime Minister of the Underworld," he became one of the most powerful and influential Mafia bosses in American history, eventually leading the Luciano crime family (later called the Genovese crime family), one of the Five Families that operates in New York.

Costello was born in Lauropoli, a mountain village in Calabria, Italy in 1891. In 1900, he boarded a ship to the United States with his mother and his brother Edward in order to join their father, who had moved to New York's East Harlem several years earlier and opened a small neighborhood Italian grocery store. While Costello was still a boy, his brother introduced him to gang activities. By age 13, Costello had become a member of a local gang and started using the name Frankie. Costello continued to commit petty crimes, and went to jail for assault and robbery in 1908, 1912 and 1917. In 1918, Costello married Lauretta Giegerman, a Jewish girl who was the sister of a close friend. That same year, Costello served ten months in jail for carrying a concealed weapon. After his release, Costello decided to avoid street rackets and use his brain to make money as a criminal. Foregoing the use of violence as a road to success and wealth, Costello claimed that he never again carried a gun. Costello would not return to jail for 37 years.

Thomas Phillip "Tip" O'Neill, Jr. (December 9, 1912 – January 5, 1994) was an American politician. O'Neill was an outspoken liberal Democrat and influential member of the U.S. Congress, serving in the House of Representatives for 34 years and representing two congressional districts in Massachusetts. He was the Speaker of the House from 1977 until his retirement in 1987, making him the second longest-serving Speaker in U.S. history after Sam Rayburn, and the longest consecutive-serving Speaker.

O'Neill was born to Thomas Phillip O'Neill, Sr., and Rose Ann (Tolan) O'Neill near Barry's Corner in the Irish middle-class area of North Cambridge, Massachusetts, known at the time as "Old Dublin." The third of three children, his mother died when he was 9 months old, and he was largely raised by a French-Canadian housekeeper until his father remarried when he was 8. O'Neill Sr. started out as a bricklayer, but later won a seat on the Cambridge City Council and an appointment as Superintendent of Sewers. During his childhood, O'Neill received the nickname "Tip" after the baseball player James "Tip" O'Neill. He was educated in Roman Catholic schools, graduating from St. John's High School in 1931, where he was captain of the basketball team. From there he went to Boston College, from which he graduated in 1936. He lived on Orchard Street in Cambridge.

John Hume (born 18 January 1937) is a former Irish politician from Derry, Northern Ireland. He was a founding member of the Social Democratic and Labour Party, and was co-recipient of the 1998 Nobel Peace Prize, with David Trimble.

He was the second leader of the Social Democratic and Labour Party (SDLP), a position he held from 1979 until 2001. He has served as a Member of the European Parliament and a Member of Parliament for Foyle, as well as a member of the Northern Ireland Assembly.

He is regarded as one of the most important figures in the recent political history of Ireland and one of the architects of the Northern Ireland peace process there. He is also a recipient of the Gandhi Peace Prize and the Martin Luther King Award, the only recipient of the three major peace awards. In 2010 he was named "Ireland's Greatest" in a public poll by Irish national broadcaster RTÉ to find the greatest person in Ireland's history.

John Hume was born in Derry and was a student at St. Columb's College and at St. Patrick's College, Maynooth, the leading Catholic seminary in Ireland and a recognised college of the National University of Ireland, where he intended to study for the priesthood. Among his teachers was the future Cardinal Tomás Ó Fiaich.