STORY: Becoming the first Western leader to address Ukraine's parliament since the start of Russia's invasion on Feb. 24, Johnson saluted the country's bravery in exploding "the myth of (Russian President Vladimir) Putin's invincibility."
"I have one message for you today: Ukraine will win, Ukraine will be free," Johnson told the lawmakers via videolink.
"This is Ukraine's finest hour, that will be remembered and recounted for generations to come," he said, echoing the words spoken by Churchill in 1940 when Britain faced the threat of being invaded and defeated by Nazi Germany.
Johnson has been one of the most passionate supporters of Ukraine's efforts to resist what Putin calls a "special operation" to disarm its smaller neighbour and protect it from fascists. Ukraine and the West say this a false pretext for an unprovoked war of aggression by Russia.
Johnson announced a further 300 million pounds ($375 million) in military aid to Ukraine, including electronic warfare equipment and a counter-battery radar system.