Unseeded at this tournament, Stephens claimed a 6-3, 6-0 victory over Keys at Flushing Meadows in just 61 minutes.

She is only the fifth unseeded female player to claim a major title in the Open era and victory continued her remarkable return from injury.

The 24-year-old only returned to action at Wimbledon after missing 11 months with a foot problem.

The pair were appearing in their first Grand Slam finals in what was the first at the US Open to feature two American women since Serena Williams beat sister Venus in 2002.

In the opening set, Stephens broke Keys' serve twice to take it 6-3.

She claimed a spectacular eight games in a row at the end of the first set and throughout the second to seal victory.

"I had surgery in January and if someone had told me then that I would win the US Open, I would have said it was impossible," said Stephens after the match.

"This journey has been incredible and I wouldn't change it for the world.

"Madison is one of my best friends on tour.

"I wouldn't have wanted to play anyone else.

"I told her that I wished it could have been a draw."

Great Britain's Jamie Murray and Switzerland's Martina Hingis added the US Open title to their Wimbledon mixed doubles crown today.

They defeated Michael Venus of New Zealand and Chinese Taipei's Hao-Ching Chan 6-1, 4-6, 10-8 in a thrilling final.

Jean-Julien Rojer of The Netherlands and Romania's Horia Tecau won the pair's second career Grand Slam men's doubles title.

The Wimbledon champions in 2015 eased to a convincing 6-4, 6-3 win over the Spanish pairing of Feliciano Lopez and Marc Lopez.

The tournament is due to conclude tomorrow with the men's singles final.

Top seed Rafael Nadal of Spain is hoping to secure a third US Open title and 16th Grand Slam crown when he faces South Africa’s Kevin Anderson.