Ukraine and Moldova started their accession negotiations towards becoming members of the European Union. Georgia received the candidate country status

Albania also started accession negotiations in 2020. Bosnia and Herzegovina became a candidate country in 2022, however the accession negotiations are blocked at the moment. Kosovo has applied for EU membership, but has yet to receive the candidate country status. Montenegro started accession negotiations in 2012 and made significant progress so far(might be joining soon). North Macedonia started accession negotiations in 2020. Serbia started accession negotiations in 2013 and made significant progress so far (they should join in the next two years).
Turkey became a candidate country in 1999, started accession negotiations in 2014 which then got suspended in 2019.
Any European country which respects EU democratic values and is committed to promoting them can apply for EU membership. To join the EU, the candidate country must fulfil a set of political and economic criteria. When negotiations on all policy areas are completed, and the EU itself is prepared for enlargement in terms of absorption capacity, then the terms and conditions for accession – including possible safeguard clauses and transitional arrangements – are incorporated into an accession treaty