The death has occurred of former United States Congressman Brian Donnelly, who passed away at his home in Cape Cod in Massachusetts on Tuesday night.
He was surrounded by members of his family, including his wife, Virginia, his daughter, Lauren and son, Brian Jr.
The Irish-American Democrat would have turned 77 today.
As the driving force behind the so-called 'Donnelly Visa' programme, Mr Donnelly secured a change to US immigration law that enabled thousands of Irish people to legally emigrate to the United States by way of a Green Card lottery.
The Donnelly Visa lottery was intended as a one-off solution to the large number of Irish who had illegally immigrated to the US, or were thinking of doing so, during the Irish economic crisis of the 1980s.
Of the 10,000 visas on offer, Irish applicants secured 4,165.
A subsequent change to immigration law established another transitional scheme running between 1991 and 1994, during which time Irish applicants secured around 40% - some 18,000 of the 40,000 visas on offer.
A permanent programme - the Diversity Visa Lottery - of 50,000 annual US immigrant visas a year selected by lottery went into effect from 1995, but the number of Irish entrants, and therefore visas drawn, fell sharply as the Irish economy grew strongly during the so called "Celtic Tiger" period.
In 2016, only 36 Irish people had obtained a US visa by lottery.
Mr Donnelly was a member of the Massachusetts State House of Representatives from 1973 to 1978, when he was elected to the US House of Representatives for the 11th District of Massachusetts.
He served as a member for six congresses, stepping down from electoral politics at the end of 1992.
In 1994, he was appointed US Ambassador to Trinidad and Tobago by President Bill Clinton.
Tánaiste and Minister for Foreign Affairs Micheál Martin has paid tribute to Mr Donnelly, describing him as a "national champion for immigration rights of Irish people living in the US, and especially undocumented Irish living and working there".
In a statement, the Tánaiste said that Mr Donnelly "worked tirelessly across the political divide to secure bipartisan agreement around a visa package that secured more than 25,000 legal residency visas to Irish citizens".
Brian Donnelly's nephew, Larry Donnelly, said he was "very sorry to confirm" that his uncle has died.
In a tweet, Mr Donnelly said he was "my uncle, my godfather and a best friend to Ireland".
Last November, the US Ambassador to Ireland, Claire Cronin, held an event honouring the former congressman and ambassador at her residence in the Phoenix Park in Dublin.
At the time, she said "thousands of Irish people benefited from his hard work".
Additional reporting Fergal O'Brien