Johnson told MPs Britain is offering "unwavering support" to Ukraine, telling the Commons "slava Ukraini", which translates as "glory to Ukraine".
He also addressed Russian citizens directly, telling them: "I cannot believe that this horror is being done in your name, or that you really want that pariah status that these actions will bring to the Putin regime."
Johnson evoked the ghost of Neville Chamberlain in an earlier video address, reminding Britons of the dire consequences of appeasement and noting his country's strong ties with Ukraine.
"And this is not in the infamous phrase 'some faraway country of which we know little'. We have Ukrainian friends in this country; neighbours, co-workers."
He was referring to comments made by Chamberlain in 1938 in which the then Prime Minister described Hitler's invasion of Sudetenland as a "quarrel in a far away country between people of whom we know nothing".
"Ukraine is a country that for decades has enjoyed freedom and democracy and the right to choose its own destiny," Johnson said.
"We – and the world – cannot allow that freedom just to be snuffed out. We cannot and will not just look away."
Johnson described Putin as a dictator and said that Ukraine and its allies would eventually prevail.
"If the months ahead are grim, and the flame of freedom burns low, I know that it will blaze bright again in Ukraine.
"Because for all his bombs and tanks and missiles, I don't believe that the Russian dictator will ever subdue the national feeling of the Ukrainians and their passionate belief that their country should be free."
'America stands up to bullies'
In remarks from the White House this morning, US President Biden joined Johnson in his condemnation of the Russian President.
"Putin is the aggressor, Putin chose this war. He and his country will bear the consequences," Biden said.
He said the actions of the US and its allies would "strike a blow" at Russia's ability to modernise its military and would be a "major hit" to Putin's long-term strategic ambitions, saying that high-tech industries would be targeted for sanctions.
"America stands up to bullies, we stand up for freedom. This is who we are."
He vowed that the war would leave Russia weaker and the rest of the world stronger.
"Liberty, democracy, human decency - these are the forces far more powerful than fear and oppression.
"They can not be extinguished by tyrants like Putin and his armies.
"In a contest between democracy and autocracy, between sovereignty and subjugation, make no mistake - freedom will prevail."
'This war is Putin's war'
German Chancellor Olaf Scholz made a televised address to the nation condemning the Russian attack on Ukraine sharply and vowed that Russian President Vladimir Putin "will not win."
Scholz said Thursday evening that "we will not accept this violation of Ukraine's sovereignty by Russia" and vowed to imply severe sanctions together with Germany's allies.
Regarding the military attack on Ukraine, Scholz stressed that Putin "is on his own. It was not the Russian people who decided to go to war. He alone bears full responsibility for it. This war is Putin's war."
The chancellor said that "Putin should not underestimate Nato's determination to defend all its members. That applies explicitly to our Nato partners in the Baltic States, in Poland and in Romania, in Bulgaria and in Slovakia. Without ifs and buts.
"Germany and its allies know how to protect themselves."
'You will see our faces, not our backs'
Ukraine's President Volodymyr Zelenskyy has addressed his nation since the attack, urging citizens with military training to make themselves available on the front lines all others to donate blood to help heal injured soldiers.
But it's the former actor's stirring speech in the hours before the invasion that has gathered the world's attention.
Recalling his efforts to communicate with Putin, he directed remarks to the Russian people themselves, calling on them to take action.
"Today I initiated a phone call with the president of the Russian federation. The result was silence. Though the silence should be in Donbass. That's why I want to address today the people of Russia. I am addressing you not as a president, I am addressing you as a citizen of Ukraine," he said.
"More than 2000 km of the common border is dividing us. Along this border your troops are stationed, almost 200,000 soldiers, thousands of military vehicles. Your leaders approved them to make a step forward, to the territory of another country. And this step can be the beginning of a big war on European continent.
"We know for sure that we don't need the war. Not a Cold War, not a hot war. Not a hybrid one. But if we'll be attacked by the [enemy] troops, if they try to take our country away from us, our freedom, our lives, the lives of our children, we will defend ourselves. Not attack, but defend ourselves. And when you will be attacking us, you will see our faces, not our backs, but our faces.
"The war is a big disaster, and this disaster has a high price. With every meaning of this word. People lose money, reputation, quality of life, they lose freedom. But the main thing is that people lose their loved ones, they lose themselves.
"They told you that Ukraine is posing a threat to Russia. It was not the case in the past, not in the present, it's not going to be in the future. You are demanding security guarantees from Nato, but we also demand security guarantees. Security for Ukraine from you, from Russia and other guarantees of the Budapest memorandum.
"But our main goal is peace in Ukraine and the safety of our people, Ukrainians. For that we are ready to have talks with anybody, including you, in any format, on any platform. The war will deprive [security] guarantees from everybody — nobody will have guarantees of security anymore. Who will suffer the most from it? The people. Who doesn't want it the most? The people! Who can stop it? The people. But are there those people among you? I am sure.
"I know that they [the Russian state] won't show my address on Russian TV, but Russian people have to see it. They need to know the truth, and the truth is that it is time to stop now, before it is too late. And if the Russian leaders don't want to sit with us behind the table for the sake of peace, maybe they will sit behind the table with you. Do Russians want the war? I would like to know the answer. But the answer depends only on you, citizens of the Russian Federation."
Additional reporting - AP, Daily Telegraph
