The project was announced by President Nikolas Sarkozy on a visit to a shipyard in Saint-Nazaire with the words: "This new sector will represent 10,000 jobs."
The French government would now "take the time" to create an offshore wind industry, Sarkozy said.
However, environmentalists are concerned that the government has already dallied too much over approving the measures - expected last September - needed to increase the share of renewables in France's energy mix.
According to the EU's 2020 objectives, member states must raise these by 20% on 1990 levels by 2020.
"It is good news," said Jacopo Moccia, a spokesman for the European Wind Energy Association. "Three gigawatts is the minimum required to kick-start the [French wind energy] industry."
"But the French authorities wasted a lot of time and delayed fully seizing the opportunities of offshore wind energy. This has slowed down the re-conversion of ports and heavy industry."
The wind farm tenders will now go out on 1 April, with a winner scheduled to be announced in early 2012.
The wind turbines, which would be installed at five sites off the country's Atlantic coast between Saint-Nazaire and Dieppe/Le Tréport, could then become connected to the grid by 2015.
Simultaneously, or sequentially, France will have to issue a second tender for 3GW of offshore wind energy to meet its goal of supplying 6GW of offshore wind energy by 2020.
"This means that the timing is very tight," Moccia said.
In total, France aims to provide 25GW of wind power by 2020, for an investment of €20 billion, so generating 23% of electricity demand from green energy.
The country could also become the third biggest EU market for offshore wind power.
French Ecology Minister Nathalie Kosciusko-Morizet's department hailed news of the tender as a rebirth for environmental projects. Industry Minister Eric Besson had tried to scale back the project to 2GW.
France is currently assembling around 30 offshore wind farms, with a collective output of 8GW. This compares with a UK government scheme to install up to 32GW of new capacity.
Similar programmes are already underway off the coasts of Germany, the Netherlands and Scandinavia.
The latest announcement will provide a further shot in the arm for the rapidly growing European offshore wind industry.