The Taoiseach Enda Kenny says it would be the making of us as a nation if the Marriage Equality Referendum is passed next month.
Mr Kenny has launched the Fine Gael party's call for a 'Yes' vote on May 22.
He says the issue is solely one of civil marriage equality and has nothing to do with church marriages.
The Taoiseach says a Yes vote would truly define our republic.
He said: "So I ask the people of Ireland to open their hearts, to be their king and generous and warm selves, as we know them to be, to look to an inclusive and compassionate future and to vote Yes.
"Yes to love, yes to respect, yes to equal rights and yes to equal marriage.
"I believe it can and will be the making of us as a nation."