Children’s Minister Katherine Zappone says she’s heartbroken at the death of her wife.
Dr Ann Louise Gilligan passed away after a short illness.
The couple had been together since 1981 and married in British Columbia in 2003.
In 2006 they launched a landmark case to have their marriage officially recognised under Irish law – which many say was the official beginning of the campaign for marriage equality in Ireland.
Speaking on the day the referendum was passed in 2015, Dr Gilligan said it was a historic moment.