The forward had emerged as a doubt for the final after picking up a slight injury against Barcelona in the Europa League on Thursday night.
During his press conference on Friday afternoon, Red Devils head coach Erik ten Hag admitted that he 'did not know' whether the England international would be fit for the final.
"I don't know. Players are now coming in, we have to do investigations, medical, of course, yesterday we did. So straight after a game most of the time you can't say, you have to wait for a 100% diagnosis. So let's do the medical, the work, we have to wait," said the Dutchman.
However, Rashford made the trip down to London on Saturday, and the 25-year-old has been named in the starting XI for the 20-time English champions this afternoon.
The Man United side shows two changes to the one that took to the field for the first whistle against Barcelona.
The first alteration is at right-back, with Diogo Dalot coming into the side to replace Aaron Wan-Bissaka.
Meanwhile, Antony's winner off the bench against the Catalan giants has earned him a spot in the XI, with Jadon Sancho dropping down to the bench.
As a result, there is more frustration for club captain Harry Maguire, with Raphael Varane and Lisandro Martinez starting in the middle of the defence, and Luke Shaw featuring at left-back.
Fred has benefited from Christian Eriksen's injury to enjoy a run in the team, and the Brazilian, who also scored against Barcelona, will feature in central midfield alongside Casemiro.
Bruno Fernandes has played off the right on a number of occasions in recent weeks, but it appears that the Portugal international will feature in central position here.
As for Newcastle, the headline team news is that there is a start for former Liverpool goalkeeper Loris Karius, with the club's number one Nick Pope suspended and the number two Martin Dubravka ineligible.
Karius makes his competitive debut for the Magpies, and it is the stopper's first competitive appearance in 728 days.
MANCHESTER UNITED XI: De Gea; Dalot, Varane, Martinez, Shaw; Fred, Casemiro, Fernandes; Antony, Weghorst, Rashford
NEWCASTLE UNITED XI: Karius; Trippier, Schar, Botman, Burn; S Longstaff, Guimaraes, Joelinton; Almiron, C Wilson, Saint-Maximin