European Union leaders have formally agreed to grant candidate status to Ukraine, as well as Moldova, although the two former Soviet republics face a long path before joining the bloc.
President of the European Council Charles Michel made the announcement on Thursday.
"Today marks a crucial step on your path towards the EU," Michel said, describing the decision as a "historic moment".
Ukraine applied to join the bloc just days after the Russian invasion on 24 February, and the process from application to candidacy has gone through at record speed.
Ukraine's President Volodymyr Zelensky hailed the news as "a unique and historic moment", adding "Ukraine's future is within the EU".
French President Emmanuel Macron said that the decision by EU leaders sent a "very strong signal" to Russia that Europeans support Ukraine's pro-Western aspirations.
President Vladimir Putin had declared Ukraine to be part of Moscow's sphere and insisted he was acting due to attempts to bring the country into NATO, the Western alliance that comes with security guarantees.
Before the invasion, European powers had distanced themselves from US support for Ukraine's NATO aspirations and EU membership can take years with no guarantee of success.
Ukraine and Moldova will have to go through protracted negotiations and the European Union has laid out steps that Kyiv must take even before that, including bolstering the rule of law and fighting corruption.
European Commission President Ursula von der Leyen said the accession process would be "merit-based" and "by the book".
Moldova's application was also accepted, but a third former Soviet state, Georgia, has still to qualify for candidacy.
Von der Leyen said all three countries were "part of the European family".
Several Western Balkan leaders at a separate Brussels summit on Thursday expressed frustration over the long process of joining the EU.
"North Macedonia is a candidate [for] 17 years if I have not lost count, Albania eight, so welcome to Ukraine," warned Albanian Prime Minister Edi Rama.
A month ago France warned that Ukraine's bid to join the EU would not be finalised for "15 or 20 years," pouring cold water on Kyiv's hopes for quick entry.
President Macron favours creating a looser and wider "European political community" to include countries waiting to join the EU or even those that have left, which for the moment includes just the UK.
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