Polls opened in Ireland on Friday for a historic referendum on allowing same-sex marriage that is backed by all the main political parties but opposed by the Catholic Church.
Voters are being asked whether to add an article to the constitution saying: "Marriage may be contracted in accordance with law by two persons without distinction as to their sex."
Polling stations will close at 2100 GMT and the result is expected on Saturday.
If the referendum is passed and once an ensuing law to support it is approved, Ireland would become the 19th country in the world and the 14th in Europe to legalise gay marriage.
Allowing gay couples to wed would be a seismic change in a country where homosexuality was only decriminalised in 1993 and where abortion remains illegal except when the mother's life is in danger.
The majority of Irish people identify themselves as Catholic, but the Church's influence has waned amid growing secularisation and after a wave of child sex abuse scandals that badly discredited the hierarchy.
The "Yes" side has been boosted by the support of sports, music and film stars including Irish Hollywood A-lister Colin Farrell and U2 frontman Bono.