Although it could take Ukraine and neighboring Moldova more than a decade to qualify for membership, the two-day EU summit decision is a symbolic step that signals the bloc's intention to reach deep into the former Soviet Union.
"Ukraine will prevail. Europe will prevail. Today marks the beginning of a long journey that we will walk together," EU foreign policy chief Josep Borrell said.
The move will kick-start the EU's most ambitious expansion since welcoming Eastern European states after the Cold War.
The EU leaders' unusually quick decision to give Ukraine candidate status was triggered by Russia's invasion. EU leaders stressed, however, that the bloc will need a major overhaul of its decision-making process before it can enlarge again - and Ukraine and Moldova will have much "homework" to do.
The EU's green light "is a signal to Moscow that Ukraine, and also other countries from the former Soviet Union, cannot belong to the Russian spheres of influence," Ukraine's ambassador to the EU, Chentsov Vsevolod, told Reuters.
"I am convinced that they will move as swiftly as possible and work as hard as possible to implement the necessary reforms, EU Commission chief Ursula von der Leyen told a news conference.
Ukrainian President Volodymyr Zelenskiy welcomed the EU's decision as "a unique and historic moment", tweeting "Ukraine's future is in the EU."
Russian President Vladimir Putin says his "special military operation" launched in Ukraine in late February was partly necessitated by Western encroachment into what Russia characterizes as its rightful geographical sphere of influence.
While Ukraine and Moldova were welcomed into the EU, Georgia will be given "a European perspective" but told it must fulfill conditions before winning candidate status.
Behind the triumphant rhetoric, however, there is concern within the EU about how the bloc can remain coherent as it continues to enlarge.
Reticence over EU enlargement has slowed progress towards membership for a group of Balkans countries - Albania, Bosnia, Kosovo, Montenegro, North Macedonia and Serbia - whose leaders met their EU counterparts in Brussels in the morning.
A draft of the summit statement showed that EU leaders will again give "full and unequivocal commitment to the EU membership perspective of the Western Balkans".
But Ukraine's fast track to formal candidate status has only served to increase their feeling of being sidelined, which carries the risk for the EU that Russia and China extend their influence into the Balkan region.
German Chancellor Olaf Scholz said this week that the EU must "reform its internal procedures" to prepare for the accession of new members, singling out the need for key issues to be agreed with a qualified majority rather than by unanimity.
The requirement for unanimity often frustrates EU ambitions because member states can block decisions or water them down.
Despite waves of crises that have rocked the EU, from migration and Britain's exit from the bloc, the union remains popular, with a survey this week showing approval for EU membership is at 15- year high.
Still, public discontent is mounting over inflation and an energy crisis as Russia tightens gas supplies in response to sanctions, issues for the second day of the summit on Friday.