Irish American philanthropist and billionaire Chuck Feeney is the key funder of the marriage equality drive in Ireland which will come to a head with a referendum on the right to marry for same sex couples on May 22.

Current polling points to a convincing victory for the same sex marriage side, but experts warn Irish referendums can be decided very late and voters swing wildly.

Feeney’s Atlantic Philanthropies have committed $475,000 to Marriage Equality Ltd the main group dealing specifically with the issue.

Feeney, the New Jersey-born billionaire, is giving away all of his money, an estimated $7.5 billion, through Atlantic.

A proud Irish American Feeney earmarked over $1 billion of that to be spent on educational, human rights and other projects in ireland. He also played a major role in bedding down the Irish peace process in Northern Ireland.

In addition to funding Marriage Equality, Atlantic has funded the main LGBT lobbying group, the Gay and Lesbian Equality Network (GLEN), to the tune of $2.5 million over the past few years.

Atlantic and Feeney identified equality in marriage as one of the key human rights issue they wished to focus on. Their funding helped pass the civil partnership act of 2010. On its website and in a video Atlantic cites other major advances including:

- Secured public referendum on civil marriage, which is scheduled for 2015

- Government creation of a Gender Recognition Advisory Group, the role of which is to make recommendations on how to proceed toward legal frameworks for gender recognition for transgender people

- Secured numerous significant changes in public policy and services to better reflect the needs of LGBT people in areas such as mental healthcare provision and bullying in the education system

- Increased capacities of the LGBT sector

Feeney, 82, a New Jersey native now resident in California, made his money as co-founder of DFS, the largest duty free empire in the world

The working class Irish kid from Elizabeth, NJ has surpassed the Rockefellers and Andrew Carnegie when it comes to charitable giving.

He invented “giving while living,” which is now all the rage. His example directly inspired Bill Gates and Warren Buffett to give it all away too.

One of his most important legacies is that he has convinced so many powerful people there are “no pockets in a shroud” and helping in the here and now is preferable to dribs and drabs over decades.

“Chuck has been an inspiration to both of us for many years and was living the Giving Pledge long before we launched this project," Bill and Melinda Gates said recently.

“He’s a true innovator and example to anyone who seeks to make the world a better place," Buffett said.