Keys, seeded 15th for the tournament, is the favourite to win her maiden Grand Slam on Arthur Ashe.
But she comes up against fellow American Stephens, who herself its seeking a first major title after recovering from a long-term foot injury.
Keys beat CoCo Vandeweghe to reach the final and Stephens knocked out veteran Venus Williams in her semifinal showdown on Friday.
When is the US Open final: Stephens vs Keys?
Sloane Stephens vs Madison Keys will only take place once the mixed doubles is over.
The US Open women’s singles final should begin as scheduled at 9pm UK time.
That is 4pm Eastern Time in the USA.
Discussing the match, former world No 1 Mats Wilander said: “It will be an interesting match because they have two completely different styles.
“It’s hard to know if Stephens is quick enough to stay in the rallies for long enough and it’s hard to know if Keys will keep away from missing after four or five shots if the ball keeps coming back.”
When is the US Open Mixed Doubles final?
Before the women’s singles final, Jamie Murray and Martina Hingis team up in the mixed doubles.
They begin their match against third seeds Hao-Ching Chan and and Michael Venus at 4pm UK time.
That’s 11am in New York.
