The news comes following a brief illness
Tributes have been flooding in for Dr Ann Louise Gilligan, the wife of Independent Minister Katherine Zappone.
Minister Zappone said she passed away after a brief illness.
In a statement, she said: "I am heartbroken following the passing of my beloved Ann Louise.
"Since 1981 she has been my love and my life-partner."
Zappone described Ann Louise as an "educator extraordinaire", with an exceptional love of children's lives - having taught at St Patrick's College, Drumcondra and DCU.
Ann Louise was also the co-founder and director of An Cosan - a centre of learning, leadership and enterprise in Jobstown, Tallaght.
"As a champion of equality, fairness and justice Ann Louise was fearless," Zappone continued. "Her courage inspired us to make the ultimate commitment with our marriage in British Columbia in 2003."
She also thanked the staff at St James's Hospital: "They provided care, comfort and support for which I will be forever grateful", she added.
Along with Zappone, Ann Louise was a prominent campaigner during the Marriage Equality referendum in 2015.
Arrangements for those who wish to remember Ann Louise will be made public in the coming days.
In a statement, Taoiseach Leo Varadkar said: "I am very saddened to learn of the death of Dr Ann Louise Gilligan.
"Dr Gilligan was deeply committed to education and equality and made a lasting contribution to Irish society, in particular as co-founder and director of An Cosan and through her work in campaigning for marriage equality."
Tánaiste and Enterprise Minister Frances Fitzgerald said: "I am deeply saddened by the death of Dr Ann Louise Gilligan. She was a champion of equality, a strong advocate for social justice and an inspirational pioneer on so many issues.
"Her deep commitment to education, equality and the rights of the vulnerable have made a significant mark on our society and will not be forgotten.
"Dr Gilligan’s contribution towards Marriage Equality, and all of the issues she fought for, means that Ireland is a more equal, more compassionate and kinder place.
"I had the great pleasure of knowing her. She was, quite simply, inspiring."
Leader of the Labour Party, Brendan Howlin, offered his sympathies to Dr Zappone and the Gilligan family.
"Many of us will remember Dr Ann Louise for her work in education through the An Cosán project, which has been transformative to so many lives in Tallaght.
"Throughout her life, Ann Louise always fought for justice and equality. In her passing she leaves behind a wonderful legacy and a distinctive mark on a more equal Ireland.
"Our thoughts are with Katherine Zappone and her family at this difficult time."
Labour Party spokesperson on Children and Youth Affairs, Jan O'Sullivan added: "Ann Louise was a champion for equal opportunity in Education during her time in St. Patrick’s College, Drumcondra and for the wider Equality agenda in her work with An Cosán and in campaigning so successfully alongside her wife Katherine Zappone in the Marriage Equality referendum.
“I first knew Ann Louise as an educationalist when I was Education spokesperson for the Labour Party and was hugely impressed by her passion for the role education plays in giving opportunity to those society frequently leaves behind.
"She had a great sense of fairness and was willing to fight for it wherever she could."
Heartbroken hearing of Ann Louise Gilligan's passing. Deepest sympathies to her wife Katherine Zappone. Their love changed Ireland forever❤️ pic.twitter.com/7faLYAbkvq— Gay Community News (@GCNmag) June 15, 2017
Fianna Fáil leader Micheál Martin said Ireland lost a fierce and dedicated campaigner for social and educational equality.
"Her work in St Patrick’s College of Education where she had a direct role in the training and development of student teachers will have a lasting impact all over Ireland.
"Later on, her role in establishing An Cosán in Tallaght supported marginalised communities in advancing their opportunities for success.
"However, it was in her public advocacy in the campaign for Civil Marriage Equality where most of us came to know and appreciate her passion, and deep love of equality and fairness.
"This is a very sad time for her family, and in particular, her loving wife and soulmate, Minister Katherine Zappone.
"My deepest sympathies go out to her, and to Ann Louise’s extended family and wide circle of friends and colleagues."
Additional reporting: Fionnuala Jones