The former world number one had not played a major tournament since claiming a 23rd title at the 2017 Australian Open, having given birth to her daughter, Olympia, in September.
Her first grand slam action in over 15 months had the Paris fashionistas in a whirl as she walked on court in a black bodysuit with a bright pink belt.
Afterwards Williams revealed: “I feel like a warrior in it, like a warrior princess, kind of.
“I’m always living in a fantasy world. I always wanted to be a super hero, and it’s kind of my way of being a super hero. I feel like a super-hero when I wear it.”
This was not quite a super hero performance, to be expected with Williams short of match sharpness and her footwork not quite there yet.
But the 36-year-old’s serve remains a formidable weapon, helping her take the first set after a tie-break.
The pair exchanged breaks in the second set, with Williams grabbing the decisive one in the seventh game before sealing a 7-6, (7/4) 6-4 victory – not bad going for her first match on clay in two years.
Maria Sharapova, meanwhile, lost six games in a row and then won the next six as she got her return to Roland Garros off to a successful start.
The Russian appeared to be cruising at 6-1, 3-1 ahead but Holland’s Richel Hogenkamp suddenly had her on the ropes, taking the second set and racing 3-0 ahead in the decider.
But Sharapova rediscovered her game in the nick of time to reel off half a dozen games for a 6-1, 4-6, 6-3 victory.
It was a sweet moment for the two-time Paris champion.
This time last year Sharapova had recently returned from a 15-month doping ban, but had not built her ranking high enough to qualify and was not offered a wild card.
But 12 months later Sharapova is back in the world’s top 30, seeded 28 at Roland Garros and a potential challenger for a third title.
“I think if there is any way to turn that match around, it’s that way,” she said.
“It’s great to be in this draw and great to be back on a court that I have had great success at.”
Wimbledon champion Garbine Muguruza got the better of Svetlana Kuznetsova in a first-round meeting of two former winners.
Caroline Garcia of France, the seventh seed, took just 58 minutes to dispatch China’s Yingying Duan 6-1, 6-0.
In the men’s section, Rafael Nadal began his campaign for an 11th French Open title with a rain-delayed 6-4, 6-3, 7-6 (11-9) win over Italy’s Simone Bolelli – his 80th victory at Roland Garros.
Resuming 3-0 down in the third set, Nadal swiftly recovered the break but was pushed hard by the world number 129.
The Spaniard saved three set points from 6-3 down in the tie-break before prevailing in damp conditions.
Nadal will play Argentina’s Guido Pella in the second round.
The former world number one will be looking to build on her long-awaited maiden Grand Slam triumph in Melbourne, but she has never reached the semi-finals at Roland Garros.
Despite being in the opposite half of the draw to three-time champion Serena, Wozniacki knows that Serena’s presence as an unseeded player will put pressure on her rivals.
“I think it’s always great to have the best players play, and it raises your level,” said the Dane.
“You have to play your best level, and I think having someone like Serena back, it’s keeping us all on our toes and we have to keep improving all the time.”
Wozniacki finally claimed her first major title this year, and admitted that it has lifted a weight off her shoulders.
“I think the biggest difference is really when I’m in here in the press conferences,” she said.
“I think that’s the biggest difference, because I’m not getting asked anymore, you know, what it takes to be a Grand Slam champion, why I haven’t gotten there yet.
“It feels amazing to have that with me now, and hopefully I can build on that.”
Wozniacki is the second seed in paris, behind only Simona Halep, who she beat in the Australian Open final and is still searching for a Grand Slam crown.
The 27-year-old showed improved form on clay 12 months ago when she was beaten in a tight quarter-final by eventual champion Jelena Ostapenko.
“I think I have proven myself that I can actually play on this surface, and, you know, it’s all about trying to get the timing and trying to get the head right, really,” she said.
Meanwhile, top-seeded Halep thinks Serena is still capable of challenging for titles, as the American prepares to make her Grand Slam return in Paris.
Williams will be playing in her first major tournament since winning last year’s Australian Open, having taken time off to give birth to her first child.
Halep, a two-time runner-up in Paris, knows that despite a lack of time on court, the unseeded Williams could prove a threat.
“It’s great for tennis that she’s back,” said Halep yesterday.
“Maybe she needs a little bit more time to get again used to the tournaments and everyday playing.
“In my opinion… She’s able to come back and to win tournaments again.
“She knows how to handle the pressure, how to handle all the situations. She’s (been) there for so many years. So I think she will come back and she will be good again.”
Williams, who opens her campaign with a first-round match against Czech Kristyna Pliskova, struggled on her return to tennis in March with early defeats in Indian Wells and Miami before taking more time off to get fully fit for Roland Garros.
The 23-time Grand Slam champion is joined in Paris by fellow former world number ones Victoria Azarenka and Maria Sharapova, with the trio playing a major tournament together for the first time since the 2016 Australian Open.
“I feel that now everyone is here (it) feels that the tournament is completed and everyone is here just to show that tennis is really nice and also that everyone can win it,” added Halep, who opens her campaign against world No105 Alison Riske.
“These girls are coming back, Vika (Azarenka), Serena, with the kids, which is amazing. Makes it a little bit different and also special.”
Novak Djokovic is confident his poor recent run of form will improve ahead of the French Open.
The former world number one, whose last Grand Slam crown came at the 2016 edition of Roland Garros, has struggled since returning to the tour at the start of the year and had surgery on his long-term elbow injury after the Australian Open.
More recently, the Serb, who has won 12 major titles, slumped to a shock defeat against Slovakian qualifier, World No.122 Martin Klizan, in the second round of the Barcelona Open – meaning he has failed to reach the last eight in any of the five tournaments he has played in 2018.
But, despite this, Djokovic believes his elbow problems are fixed and behind him, admitting that he has been playing virtually pain-free for the past month.
“I still want to continue tennis at the highest level. I am very motivated and I have always aimed high and this hasn’t changed,” the 30-year-old told reporters at his training base in Belgrade on Wednesday.
“I believe that things will sort themselves out very soon and I hope for some better results in the next few weeks.”
Djokovic added: “Basically it is now all about improving my fitness.”
Having split from coaches Radek Stepanek and tennis legend Andre Agassi last month, Djokovic has rekindled his relationship with long-time ally Marian Vajda – a man who has been a trusted figure within his team for many years.
Djokovic is scheduled to play the Madrid Open next week, where he has twice won before, and then the Italian Open straight after, according to his official website.
The French Open then commences on May 27.
Djokovic, who is currently ranked number 12 in the world, said: “We have made plans until the end of the clay season – three more tournaments ending with Roland Garros.”
“After that we will sit down again … and make further plans.”