The FAI and the IFA have announced a joint-bid to host the 2023 European Championships at a press conference in Belfast this afternoon.
FAI chief executive John Delaney made the announcement along with his IFA counterpart Patrick Nelson, with the former describing the bid as "historic" and one which would "bring significant benefits to Ireland - both north and south.
"We believe that the unique nature of our bid makes it a compelling vision for both UEFA and the wider European football family," Delaney added.
The formal bid will be submitted to UEFA next year with a decision expected in early 2020. While match venues have yet to be finalised, a number of possible venues have been suggested including the Aviva Stadium, Windsor Park, the redeveloped Dalymount Park, Tallaght Stadium, Ballymena Showgrounds and Turner's Cross.
The IRFU have also allowed the use of Thomond Park and Kingspan Stadium as potential venues.
If successful, both sides will qualify for the 12-team tournament, the rules having recently been altered to allow joint-hosts to qualify automatically.
The Republic of Ireland U21 side have yet to qualify for a major tournament, having played their first international back in 1986.
Noel King's side finished 3rd in their recent qualification group for the 2019 championships - which are to be held in Italy and San Marino - behind both Germany and Norway. Northern Ireland finished second in their qualifying group behind Spain.
Irish hopes of success may be high given that Delaney sits on UEFA's executive committee, the board which will ultimately decide on the venue.
The two associations have had a testy relationship over the years, most notably over the eligibility of Northern Ireland-born players declaring for the Republic, but Delaney insists they have been co-operating closely in recent years.
FAI chief executive John Delaney believes the symbolism of joining forces with the IFA could appeal to UEFA for the bid for the 2023 Under-21 European Championships. pic.twitter.com/lYRHAVBsOz— RTÉ Sport (@RTEsport) November 1, 2018
"Both Associations have a recent history of working together on various projects, including Third Level Football, Walking Football, and the introduction of the President's Junior Cup.
"This joint bid further strengthens that level of co-operation and co-hosting the U-21 finals in 2023 will follow on from our (the Republic of Ireland) hosting of the U-17 EUROs next summer and four games in EURO 2020 in Aviva Stadium."
IFA chief executive Patrick Nelson said that hosting the tournament would help "grow the game at all levels" on the island.
"We could not host a tournament of this scale on our own, therefore I am pleased that both Associations are working in partnership on this bid. I believe that together we can showcase the best of the game in Northern Ireland and the Republic of Ireland to the football world," he said.
Minister for Sport Shane Ross said the island is "well capable" of hosting the event.
He said: "The tournament brings together the brightest and most promising football talent from across Europe and the prospect of hosting matches here is very exciting.
"Ireland is already preparing to host the UEFA Under-17 Championship next summer and four games during Euro 2020.
"Furthermore, along with their partners in England, Scotland and Wales, the FAI and the IFA are also both participating in a feasibility study into the possibility of jointly hosting the 2030 FIFA World Cup.
"Therefore, we clearly have plenty of experience to draw upon when it comes to bidding for and hosting major international sporting events.
"Our tourism and sport infrastructure are amongst the finest in Europe and are well capable of providing all of the modern facilities required by participants and spectators alike. "