Sloane Stephens joked that she should "just retire now" after capping her incredible run at the US Open by claiming her first grand slam title with an emphatic win over Madison Keys.

Stephens was ranked No.957 in the world in July having undergone foot surgery in January but, after seeing off Venus Williams in a stunning semi-final upset, she brushed aside No.15 seed Keys in Sunday's (AEST) showpiece singles final.

Stephens needed just 61 minutes to dispatch Keys, with whom she shared a warm embrace after completing one of the most improbable grand slam triumphs.

Speaking at the trophy presentation, Stephens said: "I should just retire now. I told Maddie I'm never going to be able to top this.

"Talk about a comeback. Honestly I don't even know what to say. After I had surgery I worked super hard to get back. I just tried to keep the best attitude, I had the best team, things just have to come together. The last five weeks they really have.

"I can just say thank you to my team that stuck with me and even in the toughest times, on my worst days when I was being crazy, you guys stuck with me. I think this one's for all of us really.

"It's incredible, I had surgery January 23, if someone told me then I'd win the US Open… it's absolutely impossible.

"My journey to get here, coming back, just being able to keep it all together and have such a great team behind me, this journey's been incredible and I honestly wouldn't change it for the world."

Stephens went to sit with friend Keys before the presentation and said of that moment: "Maddie is one of my best friends on tour if not my best friend on tour, I wouldn't want to play anyone else, for us both to be here is such a special moment.

"I told her I wished there could be a draw because I wish we could have both won. I know if it was the other way around she would do the same for me. To stand her with today is incredible, that's what real friendship is."