The Lockheed Martin X-35 was the favourite to win
It beat fierce competition from its rival Boeing for the contract - which could be worth in excess of $200bn (£140bn).
The US Government wants up to 3,000 JSFs over the next 40 years to replace nearly all fighter jets currently in use.
The contract is also expected to bring big benefits to UK firms who stand to win lucrative sub-contracting orders.
"On the basis of the strength, weaknesses and degrees of risk of the program, it is our conclusion, joined in by our colleagues from the United Kingdom, that the Lockheed Martin team is the winner of the Joint Strike Fighter program on a best-value basis," US Air Force Secretary James Roche announced.
'Winner takes all'
Speculation had been mounting in the run-up to the announcement that the contract may be split between the two competitors.
But in the end just the one company was chosen.
"The winner take all strategy was the right approach," said Assistant Secretary of Defence Edward Aldridge, who is the Pentagon's chief weapons buyer.
Under the terms of the deal, Lockheed will initially get $19bn for the production demonstration phase of the fighter's development, while Pratt & Whitney will get $4bn for engine development.
But eventually the contract could be worth more than $200bn over the full production period of the plane.
Lockheed has said that if it won it could add up to 9,000 jobs at its plant in Fort Worth, Texas, which already employs 11,000.
Job cuts loom at Boeing
But it was a gloomier tale at Boeing, where the company said it could not rule out job cuts following the decision.
"I can't say there won't be layoffs because of this," said Jerry Daniels, president and chief executive of Boeing's Military Aircraft and Missile Systems said at a press conference.
Boeing is already planning to lay off up to 30,000 workers by the end of next year because of the downturn in the commercial airline industry.
A new breed of fighter
The US Defence Department gave Boeing and Lockheed $660m (£460m) in 1996 to develop prototypes of the fighter.
The new plane will be able to take off quickly, land vertically and on carrier decks, and have radar-evading capabilities.
It will replace most of the fighter jets of the US Air Force, Navy and Marines.
Britain's Air Force and Navy also want 150 of the planes, and the UK has already contributed $2bn (£1.4bn) towards development costs.