President Francois Hollande and Qatari Emir Sheikh Tamim bin Hamad Al Thani have signed a 6.3bn euro ($7.02bn) agreement for the sale of 24 Dassault Aviation-built Rafale fighter jets.
The contract - the third this year for Dassault AVMD.PA after deals to sell Rafale jets to Egypt and India - also includes MBDA missiles, and the training of 36 Qatari pilots and 100 technicians by the French military.
Officials said the accord, signed on Monday in Doha, Qatar, also provided for the training of a number of Qatari intelligence officers.
"It's a good choice," said Hollande, who had talks with Sheikh Tamim and will go on later to Saudi Arabia, where he is due to attend a summit on Tuesday of the Gulf Cooperation Council (GCC) in Riyadh.
Hollande will be the guest of honour at the meeting, according to his office. The GCC also includes Bahrain, Kuwait and Oman.
Dassault is in talks aimed at supplying 16 of the multi-role combat jets to Malaysia and has resumed discussions over potential fighter sales to another Gulf Arab state, the UAE.
Eric Trappier, Dassault chief executive, said Kuwait was also evaluating the plane.
The Qatar sale was "a good sign for all the countries of the region" because now they would see the capabilities of the aircraft, he said.
Deep economic ties
France and Qatar have deep economic ties.
French energy giant Total SA is a major player in the OPEC member's energy industry, with interests in oil and liquefied natural gas projects.
Qatari state-linked investors, meanwhile, have taken a keen interest in France, pumping cash into luxury group LVMH Moet Hennessy Louis Vuitton and football team Paris Saint-Germain.
Hollande's trip comes as France and other world powers work to finalise a lasting nuclear deal with Iran by the end of June.
Saudi Arabia and its Arab Gulf allies fear a deal, and the sanctions relief it would bring, could further embolden Iran, their regional rival.
Saudi Arabia is leading a coalition of Arab states carrying out air strikes against Iranian-backed fighters known as Houthis in Yemen, where France's only hostage, a woman kidnapped on February 24, is being held.
Saudi Arabia, Qatar and France are also members of the US-led coalition targeting the Islamic State of Iraq and the Levant (ISIL) group with air strikes in Iraq and Syria.