The Black Sea city of Odesa has made Boris Johnson an honorary citizen for his assistance to Ukraine, making him the first Briton to receive the award.
Mr Johnson is feted across Ukraine for the military help he has given the country since Russia invaded on Feb. 24
"We highly appreciate the help of your country, your prime minister," Gennady Trukhanov, Odesa's mayor, told BBC in an interview.
Britain has emerged as the country's "main ally and friend", he said. If other nations had provided similar assistance, he added, Ukraine "would have defeated the invaders a long time ago".
"I would like to emphasise that this is the struggle of the entire civilised community against fascism version 2.0, and in this struggle Mr Johnson will become the first Honorary Citizen of the city from Great Britain, for the entire existence of the award, since 1862."
British shoulder-mounted anti-tank missiles, weapons training and battlefield intelligence have been credited with helping Ukraine defend itself against Russia, which has more weapons, soldiers and tanks.
Last month, Mr Johnson also pledged to send long-range missiles to Ukraine.
Ukrainian forces fighting against Russia on the frontlines in Donbas have said that they are outgunned by around 10-to-1 by Russia and have been begging for more heavy artillery pieces.
Mr Johnson is by far the most popular Western leader in Ukraine. He was one of the first to visit Ukrainian President Volodymyr Zelensky in Kyiv and has had streets and cakes named after him. He has also invited Mr Zelensky to Britain for a state visit.
The title of "Honorary Citizen of Odesa" is the highest civic award that can be handed out by the Black Sea city. It was set up in 1862 when Odesa was part of the Russian Empire.
The city was formally established in 1794 by Russian empress Catherine the Great and was initially a free port. It was known for its diverse population mix, cosmopolitan atmosphere and ornate Italian architecture.
Odesa has come under periodic Russian bombardment during the war, including this week when missiles killed nearly 20 civilians including several children.