Serena Williams battled back from a set and break down to defeat Australia's Ashleigh Barty 3-6, 6-3, 6-4 to reach the French Open third round on Thursday.
The three-time champion and former world number one, dressed again in her all-black catsuit, is playing her first Slam since winning the 2017 Australian Open while two months pregnant.
The 36-year-old, seeking a 24th Grand Slam title, will face Germany's Julia Goerges for a place in the last 16.
If she gets past the third round, Williams could face old rival Maria Sharapova for a place in the quarter-finals.
"It's just incredible," said Williams.
"I am so happy to be back here. I lost the first set and thought I must try harder, I must try harder and then Serena came out.
"I will be back tomorrow to play doubles with Venus. I don't mind playing singles and doubles -- I will fight my heart out."
Williams, playing in her first Slam since winning the 2017 Australian Open while two months pregnant, had cruised through her opening round match against Kristyna Pliskova in what was a record 317th win at the Slams.
But Thursday was a tougher proposition for the 36-year-old American who was playing just her sixth match of 2018.
Williams appeared once again in her striking, all-black catsuit.
However, her game failed to match her impressive outfit in the first set where she was broken in the sixth game by the Australian.
Barty wrapped it up when the American netted a weary-looking forehand, the 12th unforced error of the set for the 23-time major winner.
Williams hit just three winners in the opener while 22-year-old Barty could afford to bide her time, just two winners and four unforced errors.
She was a break down again after dropping serve in the opening game of the second set.
But just as the half-full crowd enjoying the late evening sunshine in Court Philippe Chatrier anticipated a quick kill, Williams came storming back, reeling off four straight games for 4-1.
A fifth ace of the contest won her the set.
A break in the third game of the decider proved crucial and Williams, now ranked 451 in the world, claimed victory on a second match point with a sweeping, running forehand.
Sharapova, the champion in Paris in 2012 and 2014, saw off Donna Vekic 7-5, 6-4 in a tie which featured 10 breaks of serve and secured on a fifth match point.
Former world number one Sharapova, seeded 28 this year, will face Czech sixth seed Karolina Pliskova for a place in the fourth round.
"She won a big title in Stuttgart, so I have to be ready for this match and I'll be ready," said Sharapova of Pliskova, a player she defeated in their only previous meeting in the 2015 Fed Cup final.
The Russian star is playing in Paris for the first time since a quarter-final run in 2015. She served a doping ban in 2016 and was refused a wild card last year.
- Nadal breezes through -
Ten-time champion Rafael Nadal breezed into the third round and a clash against childhood friend Richard Gasquet.
Top seed and world number one Nadal, chasing an 11th title, swept past Argentinian Guido Pella 6-2, 6-1, 6-1, showing no signs of the brief struggles he faced in the first round against lucky loser Simone Bolelli.
The 31-year-old will next face home favourite, and his old junior rival Gasquet, whom he has beaten 15 times from as many meetings in professional tennis.
"Richard is a very good friend. We've known each other since we were 11 or 12 years old so it will be very special to play again against him," said the champion.
Top seed Simona Halep reached the third round with a comfortable 6-3, 6-1 win over Taylor Townsend of the United States.
Halep, twice a runner-up in Paris, will face Germany's Andrea Petkovic for a place in the last 16.
Spanish third seed Garbine Muguruza, the 2016 champion, was too strong for France's number 257 Fiona Ferro 6-4, 6-3.
Title challengers Marin Cilic and Dominic Thiem struggled into the last 32.
Third seed Cilic reached the third round for the eighth time with a 6-2, 6-2, 6-7 (3/7), 7-5 win over Polish qualifier and world number 188 Hubert Hurkacz.
Seventh seeded Thiem, a semi-finalist in 2016 and 2017, racked up his 31st win of the year.
The Austrian, the only man to beat Nadal on clay this year, saw off Greek teenager Stefanos Tsitsipas 6-2, 2-6, 6-4, 6-4 in a match which had been suspended overnight after the third set.
Comeback queen: Serena Williams celebrates after victory over Ashleigh Barty
Crowd favourite: Rafael Nadal celebrates
Sealed with a kiss: Maria Sharapova celebrates after victory over Donna Vekic in the French Open second round