The bridge is the latest in a succession of massively ambitious infrastructure projects championed by President Recep Tayyip Erdogan and the launch of the project comes a month ahead of a referendum on expanding his powers.
Authorities expect that work on the bridge will be completed in 2023, the year that Turkey celebrates the 100th anniversary of the foundation of the modern republic by Mustafa Kemal Ataturk.
Appropriately, the span of the bridge is to be 2,023 metres (6,637 feet).
The ground breaking ceremony was attended by Erdogan on the Asian side and Prime Minister Binali Yildirim on the European side of the site.
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"The bridge will be the number one in the world. It will connect Europe and Asia," said Erdogan.
The bridge is being built by a four way consortium of Turkish firms Limak and Yapi Merkezi and Daelim and SK of South Korea.
The ceremony was attended by South Korean Minister of Infrastructure and Transport Ho-in Kang.
Persian king Xerxes is said by the ancient Greek historian Herodotus to have build pontoon bridges across the Hellespont to transport his troops from Asia into Thrace in a campaign of 480 BC.
British romantic poet Lord Byron famously swam across the Hellespont in 1810, a feat repeated by ambitious modern-day swimmers in an annual race.
The area is hugely important to Turks as where Ottoman forces resisted an 1915 invasion by British, Australian and other Allied forces in World War I, known in the West as the Gallipoli campaign.
In recognition of this, the bridge will be known as the Canakkale 1915 bridge after the year and the Turkish province where it is located.
Over the last year, Erdogan has opened the first road tunnel underneath the Bosphorus and the third bridge across the Istanbul strait.