American Sloane Stephens has won her first Grand Slam title, smashing compatriot Madison Keys 6-3, 6-0 at Flushing Meadows on Sunday morning AEST.

Stephens' win caps an amazing return from injury, which saw her ranked No.957 in the world just six weeks ago.

Stephens missed much of last year due to a stress fracture in her foot and had surgery in January.

She returned to action at Wimbledon this year, losing first round, before a rapid rise back up the rankings saw her reach No.83 in the world prior to the US Open.

She became just the second unseeded female player to win the US Open in the open era, joining Kim Clijsters (2009) as the only other player to do so.

Stephens, who has a career high ranking of 11, will now move up to around 20 in the world.