Russian President Vladimir Putin and his Ukrainian counterpart Volodymyr Zelensky are meeting in Paris for their first face-to-face talks on a conflict in which more than 13,000 have died.
France and Germany are mediating.
The leaders will attempt to end five-and-a-half years of fighting in eastern Ukraine between government forces and separatist rebels backed by Russia.
It comes after a big prisoner swap and the withdrawal of Ukraine’s military from three key areas on the front line.
French President Emmanuel Macron and German Chancellor Angela Merkel are co-hosting the talks at the Élysée Palace.
Mr Zelensky’s recent military and diplomatic moves are aimed at securing peace, but there have already been angry reactions among his opponents, who have warned against conceding too much to Russia.
While it is unlikely that the formal meeting in Paris will result in a comprehensive peace deal between Kyiv and Moscow, Russia has spoken of “very cautious optimism” over the first leaders’ summit for over three years.
So how did we get here?
Mr Zelensky, a former comic actor, was elected president of Ukraine in a landslide victory in April following a campaign built around bringing peace to eastern Ukraine.
Since then, his strategy has focused on trying to restart talks with Moscow. For that to happen Mr Zelensky has had to agree to some Russian conditions, including pulling back Ukrainian troops in the eastern towns of Stanytsia Luhansk, Petrivske, and Zolote.
In June, Ukrainian troops and pro-Russian separatists withdrew a kilometre from Stanytsia Luhanska. By late October, the Ukrainians and separatists had disengaged from Zolote and early in November they pulled back from Petrivske.
Nato and Western intelligence experts have repeatedly accused Russia of sending heavy weapons and combat troops into eastern Ukraine to help the rebels.
Russia denies that, but admits that Russian “volunteers” are helping the rebels.
In September, Mr Zelensky won praise for a long-awaited prisoner swap with Russia – he described it as a “victory” that emerged from personal phone contact with the Russian president.
To pave the way for the summit, President Zelensky accepted a 2016 deal granting special status to the separatist-held parts of Ukraine’s Donbas region.
The “Steinmeier formula” aims to break the impasse over peace agreements reached at the height of the fighting. It details free and fair elections in the east under Ukrainian law, verification by the Organisation for Security and Co-operation in Europe (OSCE), and then self-governing status in return.
What triggered the deadly conflict?
Pro-Russian separatists seized control of large swathes of Donetsk and Luhansk regions in April 2014, just after Russia’s annexation of Ukraine’s Crimea peninsula.
It was an insurgency against the new pro-Western authorities in the capital Kyiv, who had ousted the pro-Russian President Viktor Yanukovych in street protests dubbed the “Maidan Revolution”.
The separatists later declared independence from Ukraine – but no country has recognised their “republics”.