The 2015 US Open was the 135th US Open. It was played on hard courts in the United States. Marin Cilic and Serena Williams were the defending champions in singles but Serena wasn't able to do a Calendar Grand Slam as she fell to Roberta Vinci in the semifinals and Cilic lost to Novak Djokovic also in the semifinals.
The first round saw a lot of upsets and retirements. The first round had a record 12 retirements, popularly due to injuries or illness; or the heat that looked similar to the 2015 MAVTV 500. The previous record was nine at the 2011 US Open. Despite winning no games, Vitalia Diatchenko retired from her match against Serena Williams because of an Achilles injury.
Many of the BATC people predicted either Serena Williams or Simona Halep as the women's singles champion. An unlikely Flavia Pennetta won the women's singles title, defeating fellow Italian Roberta Vinci in the final. Novak Djokovic defeated Roger Federer in the men's singles US Open final; they have met many times in 2015 and usually either semifinals or final. This tied the head to head record to 21-21.
- Serena Williams (Semifinals)
- Simona Halep (Semifinals)
- Maria Sharapova (Withdrew because of a leg injury)
- Caroline Wozniacki (Second round)
The event is known for Daria Kasatkina; having won the junior French Open the year prior. She made the third round as a lucky loser replacing fellow Russian Maria Sharapova. In the first round, Kasatkina caused a huge upset when she defeated a player of the same name, Daria Gavrilova (representing Australia at the majors and Russia outside the Slams); Kasatkina was ranked almost 100 places lower than her. Anett Kontaveit and Johanna Konta equalled the best performance by a qualifier at a Grand Slam. This third round result rose her ranking to number 109 in the world.
Eugenie Bouchard vs Dominika Cibulkova third round match saw one of the longest tiebreakers, 11-9 in the first set. After the match, Bouchard fell into the locker room and suffered a head injury; this looked like Justin Wilson after Pocono IndyCar 2015.
Roberta Vinci received a walkover into the quarterfinals despite Bouchard's withdrawal. Kristina Mladenovic won her fourth round match to make her first Slam quarterfinal; there is likely a high chance of both a Vinci and a Mladenovic seeding for the 2016 Australian Open. This spoiled the Bouchard-Makarova quarterfinal match that people have been predicting for.
Gilles Simon lost from two sets up to home favourite Donald Young. Denis Istomin and Jack Sock retired from their second round matches, adding it up to 14 retirements. In the second round, Adrian Mannarino led Andy Murray by two sets before Murray claimed the comeback. David Goffin's retirement in the third round against Roberto Bautista added it up to 15, tying the 2011 US Open. Jiri Vesely's third round retirement added it up to 16, a record for most retirements in a single major.
- After the US Open, Shuai Peng dropped out of the top 100 for the first time since qualification for the 2006 World Cup.
- During the tournament, Eugenie Bouchard suffered a concussion; withdrew from most of the fall season and was assured of at least unseeded for the 2016 Australian Open.
- The US Open women's singles final was unpredicted as most people predicted Serena vs. Halep.
- The US Open was known for the first Grand Slam quarterfinal of Kristina Mladenovic.
- This was Roberta Vinci's first major final and semifinal in singles.
- This was the first and only Grand Slam final Flavia Pennetta played in.
- The tournament saw a shock end for Williams' Calendar Year Grand Slam.