Brian Donnelly, a former congressman, state representative from Dorchester, and US ambassador who helped thousands of immigrants through the passage of a visa program that he sponsored, died on Tuesday at his home in East Dennis on Cape Cod. He was 76, days short of his 77th birthday.

He leaves his wife Virginia, his daughter Lauren, his son Brian, and his sister Louise Lydon, among other relatives and friends. There will be no funeral service, per his wishes.

The son of Lawrence and Louise Donnelly, Mr. Donnelly grew up in Dorchester’s St. Gregory’s parish. He was a Boston Public Schools teacher and coach who served in the Massachusetts House of Representatives from 1973 to 1978, when he began a 14-year tenure in the US House of Representatives.

A Democrat, Mr. Donnelly represented the Eleventh Congressional District, which included Boston wards 15 to 18, and the cities of Quincy and Brockton. The district was broken apart due to population loss registered in the 1990 US Census, and he did not run for reelection in 1992.

President Bill Clinton named Mr. Donnelly US ambassador to Trinidad and Tobago in June 1993. In 1998, he ran unsuccessfully for governor of Massachusetts, then retiring to the Cape, one of three places on earth that were sacred to him. The other two were Dorchester and Galway.

His nephew and godson, Larry Donnelly, a writer for the Reporter’s sister publication, Boston Irish, said that Mr. Donnelly “was a regular guy to his fingertips and not someone who put it on. He never had to fake authenticity. He was a very real politician. That’s why he was so loved by so many people.”

The former congressman was, he said, a centrist and a “Democrat of the old school who thought the party should be there for people who live paycheck to paycheck and work with their hands for a living. That was his animating principle. He wasn’t someone consumed by ideology, he wanted to get things done.”

Mr. Donnelly is remembered by many as a charismatic politician who led the creation of what’s informally called the “Donnelly Visa.” He once relayed the backstory to biographer John Farrell for a book on Tip O’Neill, the late US House speaker and Massachusetts Democrat: In the 1970s, hundreds of thousands of Irish residents fled to Boston and New York, staying on tourist visas and then illegally remaining in the United States. Many of them lived in his US House district, so, in 1986, he sought to tack on an amendment to an immigration reform bill that would “boost” the number of Irish work visas. Mr. Donnelly and other Irish-American members of Congress were initially blocked, so they decided to hold up the immigration reform bill until House leaders took up the amendment.

When Speaker O’Neill called Donnelly up to the House rostrum, Mr. Donnelly told him: “I got 10,000 illegal Irish kids living in Boston.” O’Neill agreed to the amendment, and the "Donnelly visas" were born. The legislation "eventually helped 25,000 Irish immigrants,” Farrell wrote.

On learning of Mr. Donnelly’s death, US Sen. Ed Markey, who served with him Donnelly in the State House and the US House, called him “synonymous” with Ireland.

“An indomitable spirit, an undeniable sense of humor, and an unwavering loyalty to his fellow Irish brothers and sisters,” Markey said in a statement to the Reporter. “He was a source of history, poetry, and humanity and always was deeply committed to serving his constituents. It was a joy to serve alongside him, and my deepest sympathies are with his family and loved ones.”

Mr. Donnelly’s nephew Larry, speaking by phone from Wicklow, Ireland, said the media coverage of his uncle’s death on the island has been “nothing short of extraordinary.” “He is fondly regarded in this part of the world, due to the work he did,” the nephew said.

Claire Cronin, who resigned from her state House seat representing the greater Brockton area after President Biden appointed her as US ambassador to Ireland, recalled on Twitter that the former congressman had visited Deerfield, her official residence in Dublin, last November, where he told “stories about his remarkable career. He was a great friend of Ireland.”

Ireland’s Tánaiste & Minister for Foreign Affairs Micheál Martin remembered how many Irish immigrants in the late 1980s and early 1990s were unable to access US healthcare or stay employed due to their lack of documentation. In a statement after Mr. Donnelly’s death, he said, “By delivering such a generous visa regime for the Irish at that time, he changed the lives of many Irish people, who went on to build prosperous lives in the US, and then give back to their adopted country in many ways.

“He never forgot his ancestral Galway roots and I was glad to see that he was able to undertake a visit to Ireland last year,” Minister Martin said.

During that visit, Mr. Donnelly also met with politicians and diplomats with whom he worked with in the 1980s. “It was a wonderful trip and he enjoyed it tremendously,” his nephew Larry said.