2015 US Open – Women's singles

Flavia Pennetta defeated Roberta Vinci in the final, 7–6^(7–4), 6–2 to win the women's singles tennis title at the 2015 US Open. It was her first and only major singles title, becoming the first woman to win her first major title after turning 30 years old. Pennetta was competing in her 49th major main draw, setting a record for the most appearances in major main draws before reaching a final. This also marked Pennetta's last major appearance, as she retired from the sport at the end of the year. Vinci was the first unseeded woman to reach a major final since Justine Henin at the 2010 Australian Open. The final made Italy the fifth country in the Open Era to have two countrywomen contest a major final (after Australia, the United States, Belgium, and Russia). This also marked the first final with two first-time major finalists since the 2010 French Open.

Serena Williams was the three-time defending champion, but lost in the semifinals to Vinci. Williams was attempting to become the fourth woman (after Maureen Connolly, Margaret Court and Steffi Graf) to complete the Grand Slam. Williams' defeat to Vinci is widely regarded as one of the biggest upsets in tennis history.

This marked the major main draw debut of future Australian Open champion Sofia Kenin, who lost to Mariana Duque Mariño in the first round.

Petra Kvitová became the first player born in the 1990s to reach the quarterfinals at all four singles majors.