The congregations at Dublin's two Orthodox synagogues in Adelaide Road and Terenure have agreed to amalgamate.
This will mean that the 107-year-old Adelaide Road synagogue, the oldest in Ireland, will close in June.
Both congregations met yesterday and decided "almost unanimously" in favour of amalgamation, said Mr Joe Briscoe, spokesman for the Orthodox Jewish community in the Republic, who belongs to Adelaide Road.
He said one of the last public events to be held there would be a wedding in May between two young Irish Jewish people who are returning from abroad, and have asked that they be allowed to marry in the synagogue before it closes.
He said there was a buyer interested in the synagogue, and was "pretty sure" the sale would go through.
He did not know whether the synagogue building would be retained in any development of the site. Everyone in the Adelaide Road congregation was "very, very sad" at its imminent closure.
The amalgamation has been brought about partly by the falling numbers of Jews in Dublin and Ireland generally. Estimates now put the Jewish population of the State at 1,000-1,200, with 6075 per cent aged over 50. It reached a peak of nearly 5,000 after the second World War.
Adelaide Road is the latest in a line of city synagogues which go back to one in Crane Street, off Dame Street, in the 18th century. It served what was once Ireland's largest Jewish community, in the South Circular Road.
Mr Briscoe said up to 200 people attached to Adelaide Road would now join roughly the same number at Terenure. The Terenure synagogue would be replaced by a new combined synagogue and communal centre, containing offices and a restaurant. He expected this to be completed within the next two years.
He recalled that in 1974, when Cearbhall O Dalaigh was inaugurated as president, he started a tradition of presidents coming to the Adelaide Road synagogue for a service of thanksgiving.
He also remembered the former president of Israel, Chaim Herzog, addressing the congregation from the pulpit where his father, the former chief rabbi of Ireland, had preached and presided over his bar mitzvah.
Apart from Terenure, there is also a small Orthodox synagogue in Cork and the liberal Dublin Jewish Progressive synagogue in Rathgar, which does not recognise the authority of Chief Rabbi Gavin Broder.