The 2016 champion Angelique Kerber kicks off her title defense today - and it has a tricky opening hurdle in 19-year-old Naomi Osaka, who has lost in the first round of a Slam just once in her young career. Kerber has only successfully defended a title once: Stüttgart, which she won in 2015 and 2016.
Karolina Pliskova heads into her first ever Slam as the No.1 seed today. The top seed has reached at least the semifinals in every US Open this decade; the last to fall before that stage was Dinara Safina, who lost to an unseeded 19-year-old Petra Kvitova in the third round in 2009.
2015 US Open quarterfinalist Kristina Mladenovic put together one of the strongest first halves of the season, compiling a 37-16 record through the grass season. However, her form has tailed off on the North American hard courts, and she comes into New York on a four-match losing streak. Her first opponent is no comfort: Monica Niculescu, who leads their head-to-head 2-0 and is yet to drop a set to the Frenchwoman.
There's déjà vu for Daria Kasatkina and Wang Qiang, whose first round match today will reprise their encounter in the same round last year. Wang won that 6-4, 2-6, 6-2 to inflict a first ever opening-round Slam exit on Kasatkina.
The US Open is the only Slam at which No.10 seed Agnieszka Radwanska has never reached the quarterfinals. However, she has never lost in the first round in Flushing Meadows either in 11 appearances stretching back to 2006.
Japan's Nao Hibino will be looking to win a Slam main draw match for the first time at her eighth attempt; her 0-7 record in Slam first rounds is a record among active players. Hibino, runner-up in Kuala Lumpur and Nanchang this year, has either reached the final or lost in the first round of every WTA main draw she has contested in 2017.
In April 2016, former World No.15 and five-time Slam quarterfinalist Kaia Kanepi announced that she was suffering from the Epstein-Barr virus and, though she would continue her career, admitted that she was "not able to practice and play as much as it is needed to be competitive in the highest level". However, in just her fifth tournament of 2017, Kanepi has followed two ITF Pro Circuit titles by qualifying for the US Open - marking her return to Grand Slam level for the first time in two years.
Thirty-two-year-old Kanepi squares off against Francesca Schiavone, 37, in the first round - a rivalry that dates back 12 years. The pair's first two meetings were both in Hasselt, with the Italian taking the first in 2005 and Kanepi exacting revenge a year later; Schiavone leads the overall head-to-head 4-3, though Kanepi won their last encounter five years ago in Brisbane, 6-3, 6-0.
No.20 seed CoCo Vandeweghe and Alison Riske will face off for the third time this year today. The Americans have split their other 2017 meetings, with Riske winning on the Dubai hardcourts and Vandeweghe taking the honours on the Wimbledon lawns. The pair's rivalry dates back to their days on the ITF Pro Circuit in 2008 and overall, Vandeweghe leads her compatriot 5-4.
Eighteen-year-old Anna Blinkova, the 2015 Wimbledon girls runner-up, has qualified for three out of four Slams this year - and for the second time, her first-round reward is a match with No.17 seed Elena Vesnina. The younger Russian stretched her compatriot to three sets before falling at Wimbledon.
Making her Slam main draw debut today will be Blinkova's conqueror in that Wimbledon junior final, 17-year-old Sofya Zhuk. This time last year, Zhuk was ranked No.594; since then, she's won three ITF Pro Circuit titles, including a $60,000 event in Bursa, Turkey last month, to rise to No.147.
Maria Sharapova's dramatic evening victory over No.2 seed Simona Halep had the entire tennis world hooked. Steve Tignor for Tennis.com and Simon Briggs for The Telegraph delve deeper into the spectacle of the Russian's return to the Grand Slam stage.
2017 marks the 20-year anniversary of Venus Williams's run to the final as a US Open debutante in 1997. SL Price looks back on a career marked by dignity and determination for Sports Illustrated.
Forty-six-year-old Kimiko Date announced her second retirement from the sport yesterday. Read more about the highlights of her remarkable second career in our feature on the Japanese champion.
Two former US Open champions are in action today - Angelique Kerber and Svetlana Kuznetsova - and both had championship runs to treasure.