Ukrainian ninth seed Elina Svitolina overcame a tricky first-round draw by beating seven-time Grand Slam champion Venus Williams in straight sets at the French Open.
Both players struggled on serve before 24-year-old Svitolina finished both sets stronger to win 6-3 6-3.
American Williams, 38, has not gone past the third round of a Slam since reaching the 2017 US Open semi-finals.
Svitolina will play compatriot Kateryna Kozlova, the world number 67, next.
Svitolina, 24, missed two match points before sealing victory at the third opportunity when Williams sprayed a backhand into the tramlines.
The Ukrainian, a two-time Roland Garros quarter-finalist, has seen her season disrupted by a knee injury but showed little sign of any lingering problem as she won in one hour and 13 minutes.
Yet going into the second Grand Slam of the year, she had not won not the clay - which she describes as her most natural surface - after successive defeats in Madrid and Rome.
That led to her jokingly describing the draw against the veteran American as more "punishment".
However, it was the Ukrainian who did the punishing as she managed to grind down Williams.
The pair exchanged five successive breaks of serve in their opening set, Svitolina holding for 5-3 and breaking again for a one-set lead, as 18 unforced errors flew off Williams' racquet.
And, after Williams led 3-1 following some more erratic service games, Svitolina won five successive games to continue her record of reaching the second round in each of her main-draw appearances at Roland Garros.
Svitolina wins on new 'garden' court
The first-round match between one of the game's greats and a seed rated an outside chance of winning the tournament was always going to go on one of Roland Garros' show courts.
So organisers opted to put the match on the new Court Simonne Mathieu, showcasing an arena which they say is the "only plant ecosystem of its kind in the world".
Named after France's second most successful female player, the court is semi-sunken and surrounded by four greenhouses which house tropical plants from South America, Africa, South East Asia and Australia.
However, Svitolina said walking to the court - where spectators wander freely on narrow gravel paths through the gardens - was a "little bit uncomfortable".
"Today I won and it was nice to go through the crowd, but I think when you lose that's very, very disturbing, I would say," she said.
"The court itself is beautiful. I really enjoyed the bounce of it and I think the crowd is great, especially when it's a full house."
The first match on the court was Garbine Muguruza's victory over American Taylor Townsend and the Spaniard was enthusiastic about her surroundings.
"It's in a very different place," said the former Wimbledon champion. "You don't feel like you are around a court. It's like in a garden. It's a different feeling. It's not small, but it's cosy."