The 19-year-old Canadian, who a year ago had failed to qualify for the tournament but has gone on to become the sport's brightest young star.
Medvedev moved a step closer to a potential semi-final showdown with Novak Djokovic at the Australian Open warm-up event.
The final will pit power against power when Andreescu takes on her childhood hero Williams, who claimed her first US Open title in 1999 before Andreescu was even born.
After a flawless first set from Mertens the tide turned in Andreescu's direction in the second when she fired a cross-court forehand winner to break the Belgian at love and take a 4-2 lead.
The 76kg category had eight wrestlers while the 68kg class featured nine wrestlers, where minnows like Bangladesh, Mauritius, Cameroon, Tonga and New Zealand were part of the field.
Osaka battled on gamely before retiring while trailing Kaia Kanepi 7-6(4), 3-0.
Former French Open champion Jelena Ostapenko is the latest player to withdraw from the US Open, organisers of the tennis Grand Slam confirmed on Monday.
Australian Nick Kyrgios produced another extraordinary performance to demolish compatriot Alex de Minaur 6-2, 6-3 at the Canadian Masters on Thursday, a day after stunning world number one Daniil Medvedev.
'I have so much to look forward to in 2021, including the Olympics'
Holger Rune crashed out to Yoshihito Nishioka in the ATP 250 Adelaide International 1 first round.
Canadians took to social media to hail their first tennis Grand Slam champion Bianca Andreescu after the 19-year-old's US Open win over Serena Williams.
Top seed Novak Djokovic beat Canadian Felix Auger-Aliassime 7-5, 7-6(1) to reach the semi-finals of the Italian Open on Friday and move within one win of 1,000 career victories.
Carlos Alcaraz came through a testing third round encounter against Nicolas Jarry.
'I'm so humbled by the continuous support from my fans in Rome and I look forward to making my return soon.'
The sprinter clocked her season best timing of 23.85 seconds but was unable to make it to the semi-finals after finishing seventh in Heat 4.
A clash of generations will decide the US Open on Saturday with Serena Williams taking a fourth crack at Grand Slam history against teenager Bianca Andreescu, who was not even born when the American lifted her first Flushing Meadows trophy.
An intimidating Vinesh Phogat pounced on her rivals to complete a hat-trick of Commonwealth Games gold medals while Ravi Dahiya too went unchallenged as India's wrestlers wrapped up their campaign with a rich haul of 12 medals, in Birmingham on Saturday.
Canadian teenager Bianca Andreescu's Indian Wells triumph was not shown on television in her home country but that did not dampen the excitement across a nation where the future of women's tennis is suddenly looking as bright as ever.
'Meghan Markle, my selfless friend, lives her life -- and leads by example -- with empathy and compassion'
Wimbledon debutant Eubanks ends Tsitsipas's challenge in fourth round.
Linthoi scripted history by defeating Brazilian Bianca Reis in the women's 57kg category event final on Friday.
Victoria Azarenka, 31, won a bronze medal for Belarus in singles and a gold in mixed doubles at the 2012 Summer Games in London. Angelique Kerber, 33, won the silver in singles for Germany at the 2016 Olympics in Rio de Janeiro.
Serena Williams, who had come into the first Grand Slam since in Auckland claiming her first title since becoming a mother, suffered an error-strewn 6-4, 6-7(2), 7-5 defeat by China's Wang Qiang in the third round at the Australian Open on Friday.
Kei Nishikori's hopes of playing at the US Open have faded further after the Japanese former world number four revealed he had tested positive for COVID-19 for a second time.
Images from Day 1 of the 2023 Australian Open at Melbourne Park on Monday.
'During the grass court season, I unfortunately experienced a setback with my knee, and have accepted that I must withdraw from the Tokyo Olympic Games.'
The French Open will be able to welcome only 1,000 people a day, including players, staff and organisers, down from the 5,000 spectators it had hoped for,
American Serena Williams has also said that the dropouts will not take the shine off a potential record-equalling 24th Grand Slam title for her.
Raducanu retires in Rome as back injury persists, Jabeur survives early scare
Dowse said that the women's competition will see 10 former Grand Slam champions, including 23-time major winner Serena Williams, along with 81 of the top 100. In the men's event, seven of the world top ten are competing.
A summary of Friday's action at the US Open.
Images from Day 3 of the 2023 Australian Open at Melbourne Park on Wednesday.
Opportunity knocks for Serena Williams on the grass courts of Wimbledon next week when she faces a diminished field on her best surface at the famous All England Club.
This year's Australian Open will be allowed to admit up to 30,000 fans a day, around 50% of usual capacity, amid the COVID-19 pandemic.
Serena Williams, who has a history of blood clots and pulmonary embolisms, said she has concerns over travelling to New York and is living in a rented house instead of the official players' hotel as a precaution.
Mickey Contractor brings the ladies together.
Belinda Bencic reached her first-ever Grand Slam semi-final on Wednesday, fending off Donna Vekic to win 7-6(5), 6-3 in their US Open last-eight clash.
