Total and Qatar Petroleum today unveiled a 25-year joint venture to develop the vast offshore Al-Shaheen oil field.
The firms' bosses told a Doha press conference that their North Oil Company would operate the field from July 14.
"Joining Al-Shaheen is a major milestone and accomplishment in the long history of the group's partnership with Qatar," Patrick Pouyanne, chairman and chief executive of Total, told reporters.
"Qatar is very important to Total, that is very clear," he said.
Total, which holds a 30 per cent stake in the North Oil Company to state-owned QP's 70 per cent, will take over operations from Maersk Oil.
The deal comes just over a week after the French energy giant defied US pressure by signing a multi-billion dollar gas contract with Iran, the first by a European firm with Tehran in more than a decade.
The Al-Shaheen field, some 80 kilometres off Qatar's northeastern coast, sits atop the North Field, one of the world's largest oil and gas fields.
The head of QP, Saad Sherida Al-Kaabi, said the deal reflected his company's desire to expand over the coming years.
"Qatar Petroleum is going to be much, much bigger than we are now," he said.
He later told AFP that his company would be looking to work with "good partners".
"We are looking everywhere in the world. Our method is working discreetly," he said.
While the contract was announced last year, the project's launch comes amid the worst diplomatic crisis in years to hit Qatar, the world's largest exporter of natural gas.
Saudi Arabia, the United Arab Emirates, Egypt and Bahrain last month cut diplomatic, political, and economic ties with the emirate, which they accuse of supporting Islamist extremism.
Doha denies the accusations.