The often loose-tongued and bungling Johnson made the eyebrow raising suggestion at Thursday's Franco-British summit, held at a British army base.
Johnson, who along with Theresa May had thrashed out a new summit with French president Emmanuel Macron, championed the idea of a bridge over the English Channel.
"Our economic success depends on good connections," he said, suggesting the Channel Tunnel should only be considered a "first step".
In a tweet Johnson said: "I’m especially pleased we are establishing a panel of experts to look at major projects together. Our economic success depends on good infrastructure and good connections. Should the Channel Tunnel be just a first step?"
Johnson has long championed the idea of a road tunnel under the Channel but was ridiculed for suggesting a new London airport could be built on an Island in the Thames estuary.
Responding to the idea of a bridge spanning 35km across La Manche, Emmanuel Macron reportedly answered positively saying: "Let's do it."
En marche ! Great meetings with French counterparts today pic.twitter.com/D73B1rSkd3— Boris Johnson (@BorisJohnson) January 18, 2018
That would no doubt be music to the ears of the tens of thousands of British tourists who head across the Channel each year, either by car ferry or via the Eurotunnel rail link. Imagine the delight among truckers too if they could simply drive across the Channel rather than queue up to get on a train.
It would certainly make transporting the Bayeux tapestry across to the UK a lot more feasible.
In fact the idea of a bridge across the Channel is nothing new. In 1981 transport officials actually submitted plans to build a €3 billion three lane motorway over the water.
At the time, engineering group LinktoEurope suggested motorists would pay a £5.60 toll charge and lorries £8 to cross, which would bring in a revenue of £220 million a year (back in 1981).
However the proposal was turned down after it was deemed "impractical", partly because of the fact that the huge pylons on which the bridge would have to be built having the potential to make navigation of the busiest shipping lane in the world difficult for vessels.
There are also the weather and security factors that mean building a bridge has never been a priority.
Reacting to Johnson's suggestion, engineers have said the idea of a bridge would be difficult but not out the question.
Mark Hansford editor of New Civil Engineer magazine told The Local: "Yes it's feasible. You look around the world and there are plenty of examples of bridges of this length particularly in South East Asia.
"It would be a magnificent iconic structure and a fantastic symbol of unity in a post-Brexit world.
"The flipside is that it would come at a cost, so the question would be who is going to fund it? The Channel Tunnel is amazing but the project ran into financial troubles twice during construction."
"It would certainly have to be a toll road to make the costs stack up."
Speaking to BBC Radio 4's Today programme, bridge designer and former president of the Institution of Structural Engineers Ian Firth said it would be a "huge undertaking, but absolutely possible".
Technical editor of New Civil Engineer magazine Dave Parker suggested the concerns around the impact on shipping could be overcome by building two islands in the channel, with the road crossing passing through a tunnel between them.
That would create a narrow shipping channel which boats could pass through.
Others poured cold water on Johnson's plan.
The joint declaration after Thursday's summit said: "The United Kingdom and France have a long history of collaboration in delivering cutting-edge technologies.
"Whether pioneering supersonic travel or better connecting our countries through the Channel Tunnel, cooperation between our nations has produced radical innovation."
Watch this space.