It will be the fourth Grand Depart to be held abroad in five editions with 2022 in Copenhagen, 2023 in Bilbao and the upcoming 2024 edition due to embark July 21st from Florence.
Barcelona Mayor Jaume Collboni was present at the announcement and his city hopes to unveil the refurbished cathedral Sagrada Familia in 2026 too.
ASO director Christian Prudhomme insisted the Tour would always respect its roots and visit the smaller towns and villages, but said he was delighted with the 2026 venue.
"Barcelona is a prestigious city and it is a city of sport," Prudhomme told AFP of what will be the 113th edition of the Tour.
He said two complete stages would take place in Catalonia and the third stage would also begin there before crossing into France.
He was excited about the platform a city such as Barcelona would provide for the build-up to the so-called Grand Depart in terms of global television audiences.
"These types of Grand Depart make the Tour de France glisten even brighter," said the man who has grown the Tour's brand over recent years.
Cycling's most famous race started in San Sebastian in 1992 and in Bilbao last year.
Next year the Tour starts in the northern French city of Lille.
The 2024 Tour de France will end in Nice on July 21st in a change from its normal route because of the preparations for the Olympics in Paris.
