President Volodymr Zelensky said his government had won freedom from Russian custody for 215 Ukrainian and foreign citizens, with the help of Turkish and Saudi mediation efforts.
He said many were soldiers and officers who had faced the death penalty in Russian-occupied territory.
Of the total, 200 Ukrainians were exchanged for just one man — pro-Russian opposition leader Viktor Medvedchuk, who is Ukrainian.
The 68-year-old oligarch escaped from house arrest in Ukraine several days before Russia’s invasion on February 24th but was recaptured in April.
He faced up to life in prison on charges of treason and aiding and abetting a terrorist organisation for mediating coal purchases for the separatist, Russian-backed Donetsk republic in eastern Ukraine.
Russian officials did not immediately comment on what appeared to be the biggest prisoner swap of the nearly seven-month war.
Russian President Vladimir Putin is believed to be the godfather of Mr Medvedchuk’s youngest daughter, and his detention sparked a heated exchange between officials in Moscow and Kyiv.
He is the head of the political council of Ukraine’s pro-Russian Opposition Platform-For Life party, the largest opposition group in Ukraine’s parliament. The government has suspended the party’s activity.
“It is not a pity to give up Medvedchuk for real warriors,” Mr Zelensky said in his nightly video speech.
“He has passed all the investigative actions provided by law. Ukraine has received from him everything necessary to establish the truth in the framework of criminal proceedings.”
In another swap, Ukraine won the release of five commanders who led Ukraine’s defence of the Azovstal steel plant in Mariupol in exchange for 55 Russian prisoners it was holding, Mr Zelensky said.
More than 2,000 defenders, many from the Azov Regiment, marched out of the Azovstal steel plant’s twisted wreckage into Russian captivity in mid-May, ending a nearly three-month siege of the port city of Mariupol.
Mr Zelensky said the five leaders, including regiment commanders Denys Prokopenko and Svyatoslav Palamar, are in Turkey, where they will remain as part of the deal “in complete safety” until the end of the war, under the protection of Turkish President Recep Tayyip Erdogan.
The complex prisoner swap also brought the release of 10 foreigners, including five British nationals and two US military veterans who had fought with Ukrainian forces.
They were released by Russian-backed separatists as part of an exchange mediated by Saudi Arabia, US and Saudi officials said.
The Britons included Shaun Pinner and Aiden Aslin.
UN secretary-general Antonio Guterres welcomed the exchanges, calling them “no small feat”, but added that “much more remains to be done to ease the suffering caused by the war in Ukraine”, his spokesman said.