The Prime Minister, making his last visit to Ukraine before leaving office, said the UK “will continue to stand with our Ukrainian friends” as he set out a further £54million package of military aid.
Mr Johnson’s visit came as Ukraine marked 31 years since its independence from Moscow’s rule.
And it also came six months on from Russia's invasion of Volodymyr Zelenskyy's nation.
The Prime Minister will leave office on September 6, the day after either Liz Truss or Rishi Sunak emerges as the victor in the Tory leadership contest.
He said in Kyiv today: “What happens in Ukraine matters to us all.
“That is why I am in Kyiv today. That is why the UK will continue to stand with our Ukrainian friends. I believe Ukraine can and will win this war.”
The Prime Minister used his meeting with Mr Zelenskyy to set out a further package of military aid, including 2,000 drones and loitering munitions.
He also received the Order of Liberty, the highest award that can be bestowed on foreign nationals, for the UK’s support for Ukraine.
Mr Johnson said: “For the past six months, the United Kingdom has stood shoulder-to-shoulder with Ukraine, supporting this sovereign country to defend itself from this barbaric and illegal invader.
“Today’s package of support will give the brave and resilient Ukrainian armed forces another boost in capability, allowing them to continue to push back Russian forces and fight for their freedom.”
The package includes 850 hand-launched Black Hornet micro-drones – smaller than a mobile phone – which can be used to provide live feeds and still images to troops, particularly important in urban warfare.
The support also includes larger drones and loitering weapons, which can be used to target Russian vehicles and installations.
The UK is also preparing to give mine-hunting vehicles to operate off the coast, with Ukrainian personnel being trained in their use in UK waters in the coming weeks.
Ukraine’s ambassador to the UK Vadym Prystaiko marked the occasion by urging UK citizens to be “patient” as the war-torn country “cannot afford to lose your support”.
He said: “You are playing a very important part in this fight. Ukraine will do what it takes to claim victory."
Boris Johnson with Volodymyr Zelenskyy in Kyiv Ukrainian Presidential Press Office
Mr Johnson in Kyiv Ukrainian Presidential Press Office