Public backing for same-sex marriage in a referendum is important to show the Republic of Ireland is "very tolerant and inclusive", said Taoiseach Enda Kenny as he announced a date for the vote.
Speaking on RTE's Prime Time TV show on Thursday night he said he expected the referendum to be held on May 22.
Mr Kenny said: "I hope it will go through, this about tolerance, respect, understanding and sensitivity."
He said most politicians in the Irish parliament "are very much in favour of this".
The Taoiseach added: "It's a question that will be put very clearly to the people. I support this very strongly. It sets out our image of a very tolerant and inclusive Ireland.
"I do hope the support holds up and that the referendum is passed and adopted by the people."
He said he expects the vote to be on May 22.
Last month the Irish Cabinet approved the wording for the referendum.
Frances Fitzgerald, Minister for Justice and Equality, said the wording will read: “Marriage may be contracted in accordance with law by two persons without distinction as to their sex.”
The referendum in the spring will be held alongside a vote to reduce the age from 35 to 21 for those wishing to become Irish President.