Williams stretched her winning streak to 19 matches against Sharapova and now leads their head-to-head series 20-2.
"Every time I come up against her," Williams said, "I just bring out some of my best tennis."
Sure did this time; the whole thing lasted all of 59 minutes. Williams won twice as many points, 56-28. She saved all five break points she faced and lashed serves at up to 115 mph. She broke five times.
Few players would have stood a chance against Williams the way she performed — and certainly not a diminished Sharapova, who is ranked just 87th after missing much of this season with a bad right shoulder.
"She would win the title, playing like this," 18-time major champion Chris Evert said about Williams on ESPN's telecast.
Williams arrived at Flushing Meadows, where she's won six titles, accompanied by questions about her back, because spasms that flared up earlier this month forced her to stop playing during the final of one hard-court tuneup tournament and pull out of another one entirely.
Didn't seem to be an issue against Sharapova.
Not one bit.
"The body's good. I feel good," Williams said. "My back's a lot better. So I'm excited. This is going to be fun."
A year ago, she was beaten by Naomi Osaka in straight sets in a U.S. Open title match that devolved after a back-and-forth between Williams and chair umpire Carlos Ramos. He warned her for receiving coaching signals, which isn't allowed in Grand Slam play; when she later broke a racket, he docked her a point; when she argued with him and called him a "thief" and a "liar," he docked her a game. The U.S. Tennis Association decided that Ramos would not officiate any match involving Serena Williams or her older sister, Venus, at this year's tournament.
Williams was calm and cool as can be against Sharapova, only rarely showing the slightest hint of emotion with a cry of "Come on!" or by raising a clenched left fist after the shot of the night, a backhand passing winner that saved a break point early in the second set.
"That was definitely a big point for me," Williams said. "She's the kind of player that gets momentum and she starts going. I was really excited that I hit that winner."
It shaped up, at least, as far and away the most intriguing matchup on Day 1 at the year's last Grand Slam tournament.
Few athletes in any sport have been as popular in recent decades.
Williams owns 23 major singles title, Sharapova five.
Both have a career Grand Slam.
Both have been ranked No. 1.
So, yes, there were plenty of other matches around the grounds Monday, with No. 1 Novak Djokovic opening defense of his title with a 6-4, 6-1, 6-4 victory over Roberto Carballes Baena, and 21-year-old American Reilly Opelka providing the biggest upset of the afternoon in his U.S. Open debut by eliminating No. 11 Fabio Fognini of Italy 6-3, 6-4, 6-7 (6), 6-3.
And, sure, 2016 champion Angelique Kerber continued her rough Grand Slam year with a first-round exit against Kristina Mladenovic by a 7-5, 0-6, 6-4 score, while 2016 runner-up Karolina Pliskova and reigning French Open title winner Ash Barty both struggled through rough starts before emerging to win.
The Williams family only dropped a total of three games in two matches Monday, because Venus beat Zheng Saisai 6-1, 6-0 earlier.
Nothing brought out the spectators the way Serena Williams vs. Maria Sharapova did, with full-throated roars greeting them when they walked from the locker room into a dimly lit stadium.
When the lights came on, Williams proved far more ready for prime time.
Only once before had Sharapova lost a night match in Arthur Ashe Stadium.
"I've had a lot of tough matches here and a lot of tough losses," she told the crowd afterward, "but coming out here tonight makes it all worthwhile."