Bulgaria became the 21st official member of the eurozone on 1 January but who will be next to join the single currency?
The euro entered into circulation in 1999 and all new members of the European Union are obligated to join the single currency once they pass a set list of monetary health checks and meet certain criteria.
Bulgaria took its time joining the eurozone: throughout the 2010s shortly after the nation joined the EU in 2007, successive governments tried and failed to get the Bulgarian lev into a fit enough state to join the so-called euro waiting room, the ERM II.
After a significant delay, Bulgaria finally applied to join ERM II in 2020 and was admitted alongside Croatia. However, unlike Croatia, which adopted the euro in 2023, Bulgaria has had to wait longer before getting the green light.
It means that there are just six EU members left that are not part of the eurozone, begging the question which – if any – will be next to join?
For the time being, it is safe to assume that Denmark will keep using the kroner, as it has an official opt-out from joining the euro.
A referendum is needed to scrap that free-pass but given Denmark is slightly preoccupied with Donald Trump’s Greenland antics, there will probably be no cashing in of political capital anytime soon to organise one.
Denmark’s neighbour, Sweden, has no such opt-out and is essentially deliberately failing to meet the ERM II criteria on purpose. Public support for joining has steadily increased but again a referendum would be needed to take the next step.
No political party has signalled that it will make this a priority as support for membership is not overwhelming or significant enough where it cannot be ignored.
Czechia and Poland are also unlikely to join soon, as polls regularly show that there is no majority in favour of ditching the crown or złoty.
Hungary and Romania are interesting cases, as there is a majority of support in those countries for euro adoption.
Long-time government leader Viktor Orban has resisted calls to join the eurozone, refusing to forge closer ties with the EU. But a change of prime minister might well be in the offing and a potential Orban-successor might make it a priority.
Whether the forint is healthy enough for Hungary to actually join is another question entirely.
In Romania’s case, near consistent political instability over the last decade has prevented the required monetary stability needed to join ERM II. That is again unlikely to change anytime soon.
It is not impossible that the next official user of the euro might actually be a country that is not currently an EU member.
Montenegro is widely considered to be the most promising EU candidate and currently already uses the euro, albeit in a rather unofficial capacity. The Adriatic nation used to use the German mark but switched to the euro when Germany adopted the single currency.
Kosovo also uses the euro but Cyprus, Greece, Romania, Slovakia and Spain still refuses to recognise its independence, meaning there is little to no prospect of EU membership in the near future.
Another potential euro-user could be Iceland, whose government coalition has pledged to organise a referendum on restarting EU membership talks before 2027. Public opinion is still divided but the quickly changing geopolitical situation might prompt a change of heart.
Norway too might find itself in a situation where eurozone and/or EU membership is appealing. For the time-being, public support can be best described as maybe ‘Euro-curious’ at best.
One country that will almost certainly never join the euro is the United Kingdom, which had an opt-out of its own while a member of the EU.
Although Prime Minister Keir Starmer has acknowledged that further talks about aligning closer with Brussels on issues of national interest will happen in 2026, the prospect of monetary union is a near impossibility.
As far as the eurozone shrinking is concerned, a long time has passed since its members were genuinely considering ejecting Greece during the worst days of the financial crisis.
Nobody for the moment at least finds themselves in similar perilous circumstances and Greece’s subsequent recovery lends credence to the idea that the right decision was ultimately made.
The European Central Bank still maintains that leaving the eurozone voluntarily is not legally possible as monetary union is considered to be irreversible in that regard.
