New Zealand's Lulu Sun has won her first round at a US Open.
But it took three sets to beat her opponent, Camilla Osorio, 6-4, 2-6, 6-0 this morning (NZ time).
The Colombian had to take a medical time out after falling and hurting an ankle.
Today's win broke the Kiwi's grand slam drought, as the last time she made to a second round was at Wimbledon last year.
The 23-year-old plays her second round match on Thursday (NZ time). Her world ranking is 164.
The tournament at Flushing Meadows in New York began a day earlier than usual on Sunday.
Under the new extended 15-day format, first-round singles action will be contested from Sunday to Tuesday, rather than two days as in previous years, spreading out the star attractions and allowing access for another 70,000-odd spectators.
Sabalenka was among the marquee names on the opening day's schedule and the Belarusian fed off the vocal Arthur Ashe crowd to overcome determined Swiss Rebeka Masarova 7-5 6-1 and move into the next round.
"When I won that first set and you cheered for me, I got goosebumps," said Sabalenka, who will take on Russia's Polina Kudermetova in the second round on Wednesday.
"Your support means a lot to me, thank you for coming. It was an amazing atmosphere."
In a surprise upset, Alexandra Eala became the first Filipino player to win a main draw match at a Grand Slam in the professional era, as she beat 14th seed Clara Tauson.
The 20-year-old burst into tears amid raucous support from the Grandstand crowd as she produced a stunning comeback from 5-1 down in the third set to beat the Dane 6-3 2-6 7-6 (11) after Tauson had twice served for the match.
"I'm so blessed to be the first to do this," she said afterwards. "It makes what I do bigger than myself, and it ads meaning to what I do.
"This match is one for the books for me."
Djokovic battles past Tien
Novak Djokovic delivered a lesson in Grand Slam tenacity to Learner Tien, battling past the American teenager 6-1 7-6(3) 6-2 to launch his latest quest for a record 25th major title.
Competing in his first singles match since his run to the Wimbledon semi-finals last month, the 38-year-old Serb swapped the whites for a sleek all-black outfit and fought through physical issues to secure his 80th win at Arthur Ashe Stadium.
Victory also meant Djokovic became the first player since the sport turned professional in 1968 to win 75 straight opening-round matches at the Grand Slams, with 55 of those wins coming in straight sets.
The seventh seed shrugged off a time violation to consolidate an early break at the start of the contest and a heated debate with the chair umpire shortly afterwards only spurred him on to wrap up the opening set in double quick time.
The 19-year-old Tien, on a near-impossible mission to hand Djokovic his first opening-round loss at a Grand Slam since the 2006 Australian Open, had his chances to draw level during a draining second set but crumbled in the tiebreak.
After treatment for a nasty right foot blister, Djokovic produced some heavy groundstrokes from the baseline to break for a 3-1 lead in the third set and the four-times New York champion never looked back from there.
Compelling wins
Earlier, the extra crop of local ticketholders witnessed compelling wins from 2024 finalist Taylor Fritz, who beat compatriot Emilio Nava 7-5 6-2 6-3, and 2023 semi-finalist Ben Shelton, who beat Peru's qualifier Ignacio Buse 6-3 6-2 6-4.
Fourth seed Fritz and the sixth seed Shelton emerged as two of the brightest hopes to end a 22-year US men's drought at their domestic major, as their women's counterparts have long carried the torch for American tennis.
Briton Raducanu, the first qualifier to win the tournament four years ago, made the second round for the first time since hoisting the trophy as she defeated Japanese qualifier Ena Shibahara 6-1 6-2.
"I did feel different coming into it this year," said Raducanu, who lost in the first round in 2022 and 2024.
"I felt like I was doing the right things day to day, but still, it's in the back of your head. So I'm just very pleased to have overcome that."
Canada's Leylah Fernandez, who lost to Raducanu in the final four years ago, defeated compatriot Rebecca Marino 6-2 6-1 while 2023 Wimbledon champion Marketa Vondrousova saw off Oksana Selekhmeteva 6-3 7-6(3).
Former French Open winner Jelena Ostapenko made smooth progress with a 6-4 6-3 win over Chinese qualifier Wang Xiyu.
Qualifier Janice Tjen earned Indonesia's first win in a Grand Slam main draw in 22 years when she knocked out 24th seed Veronika Kudermetova 6-4 4-6 6-4.
