"Norway today commenced the largest public procurement project in its history," the government said in a statement.
Defence Minister Espen Barth Eide hailed the 60-billion-kroner ($10-billion) deal for a total of 52 jet fighters.
"The F-35, which Norway selected in 2008, represents a completely new generation of combat aircraft that will form a corner stone of the future Norwegian Armed Forces," he said in the statement.
Norway agreed in 2008 to buy 52 Lockheed Martin-built F-35A Lightning II planes from the United States, but had put off placing its orders until it got the green light from US authorities to integrate a Norwegian-made weapons system into the plane earlier this week.
"We will begin preparations for the final phase of Joint Strike Missile (JSM weapons system) development after receiving confirmation from US authorities of their support for the integration of the missile into the F-35," Barth Eide said.
"Securing such support has been an important precondition for many of our partner nations before they would themselves commit to supporting the JSM," he said.
While securing US support does not automatically mean that the Norwegian missile system will be integrated into all F-35s, Oslo voiced optimism that other users of the planes would opt to take it.
"Total market potential for the JSM is estimated to be between 20 and 25 billion kroner," the government said.
It said the two planes authorized on Friday would be joined by two more in 2016, and would be based in the United States "as part of a joint partner training centre".
"They are to be followed by up to 48 additional aircraft from 2017 that are to be based at Ørland Main Air Station in central Norway," it said, adding that the overall cost of the procurement phase of the project was estimated at 60 billion kroner.
"Norway's parliament yesterday approved a significant increase in defence spending in order to finance the purchase and to increase the general operating budget of the armed forces," Barth Eide said.