Williams, beaten by Angelique Kerber in the Wimbledon final in July, won 6-3 6-0 against Latvian 19th seed Sevastova.
Victory will equal Margaret Court’s record of 24 Grand Slam singles titles.
“It is really incredible. A year ago I was literally fighting for my life at the hospital after having the baby,” said Williams, who missed last year’s US Open because of the birth of her child, Olympia.
“Every day I step out on this court I am so grateful to have an opportunity to play this sport.
“So no matter what happens in any match, I already feel like I have already won.”
Serena in stats
- The American will compete in her 31st Grand Slam final and ninth US Open final.
- Having lost her past two semi-finals at Flushing Meadows, Williams will make her first appearance in the final since beating Caroline Wozniacki in 2014.
- The 17th seed has won the US Open a record-equalling six times – the same amount as compatriot Chris Evert.
- Williams will be the third oldest women’s Grand Slam finalist in the Open era and, if she wins, the oldest champion, overtaking her own record set at the 2017 Australian Open.
Williams close to her very best
Williams was out of the game for over a year after announcing her pregnancy in April 2017 and then giving birth last September.
Now, she is back playing at her home Grand Slam and looking close to her very best.
A dominant win over older sister Venus laid down a significant marker in the third round, before a straight-set win over Czech eighth seed Karolina Pliskova in the quarter-finals showed she was able to compete with the world’s best players once again.
But the ease with which she ran away with the match – winning 11 of the final 12 games and losing just 12 points in the second set – was startling.
“This is just the beginning. I’m only a few months in and really looking forward to the rest of the year and next year,” Williams said.
“I just feel like there’s a lot of growth still to go in my game. That’s actually the most exciting part.
“Even though I’m not a spring chicken, I still have a very, very bright future.”
Attacking Williams blunts Sevastova
Williams made a slow start in front of an expectant crowd on Arthur Ashe Stadium, which had the roof closed because of rain and thunderstorms.
She lost her serve in the first game and trailed 2-0 before winning four in a row to take command.
I just usually come in to shake hands. I wanted to try something different and it worked in my favour
Williams started to find her range and her power could not be contained by Sevastova.
More striking was the former world number one’s willingness to come forward, approaching the net on 28 occasions and winning 24 of those points.
Once she took the first set in 39 minutes there was no way back for her 28-year-old opponent.
Williams hit 14 winners in the 25 points she needed to take the second set in 27 minutes.
“I’ve been working hard on my volleys,” Williams said of her aggressive gameplan. “I have won a few doubles championships, so I know how to volley.
“I just usually come in to shake hands,” she joked. “I wanted to try something different and it worked in my favour.”
Sevastova, who beat defending champion Sloane Stephens to reach the last four, said: “When she’s in front it’s tough to play. I tried on her games, but she served well – when somebody serves an ace at 123 miles per hour there’s not much you can do.”
Open era’s oldest Grand Slam women’s finalists
As Williams said in the aftermath of victory, she usually only comes into the net to shake hands. She is a very fine doubles player, but in singles her domination from the back of the court is normally more than sufficient.
But in this semi-final, to counteract Sevastova’s fondness for a drop shot and a sliced approach, Williams virtually camped at the net and barely missed a drive volley winner.
This was the six-time champion’s sixth commanding performance of the fortnight. She will take some stopping in the final.