Johnson had spearheaded the leave campaign and spoke from Leave HQ just after 11am to share his delight at the referendum result, calling it a 'glorious opportunity'.
The dramatic final result of the EU referendum was announced in the early hours of Friday morning and revealed Britain had voted to leave the 28-state union by a margin of over 1million votes.
'A brave and principled man'
Uxbridge and South Ruislip MP Johnson said: “I want to begin by paying tribute to David Cameron.
“He is one of the most extraordinary politicians of our age, a brave and principled man.”
He added that while he was 'sad' the Prime Minister would be stepping down he 'respected his decision'.
Speaking alongside fellow leave campaigners Michael Gove and Labour MP Gisela Stuart, Johnson then turned his attention to the result itself, saying the outcome 'does not mean the United Kingdom will be any less united'.
The comments came just minutes before Scottish First Minister Nicola Sturgeon said a second referendum on Scottish independence would be 'highly likely' in light of Brexit.
'One of the toughest questions of all'
Johnson said: “This year we gave [the public] one of the biggest and toughest questions of all.
“There is no way to have dealt with a decision of this scale except by putting it to the people.
“I think the electorate have searched in their heats and answered as honestly as they can.”
The former Mayor of London is the bookies favourite to be the next Prime Minister after Cameron steps down later to this year, with odds of 8/11.
He is followed by Home Secretary Theresa May with 9/4 and Michael Gove at 5/1.
Cameron address the country's press outside Downing Street just after 8am on Friday morning to announce he would not be leading Britain through Brexit, and said he expected a new leader to be chosen by October.
Johnson added: “I want to reassure everybody that in my view, as a result of this Britain will continue to be a great European power.
“But there is simply no need in the 21 century to be part of a federal system of Goverment.
“We can pass our laws and set our tax.”
“We can control our borders.”
'We can be very proud'
During the speech at Leave HQ in central London, Johnson made no reference to his leadership ambitions.
But he died attempt to reassure young people that Britain could 'look forward' to the country's future outside of the union.
He said: “It is the essence of our case that young people in this countryr can look forward to a more secure and more prosperous future if we take back the democratic control that is the foundation of our economic prosperity.
“I think we can be very proud of the result.”