2021 US Open (tennis)

The 2021 US Open was the 141st edition of tennis's US Open and the fourth and final Grand Slam event of the year. It was held on outdoor hardcourts at the USTA Billie Jean King National Tennis Center in Flushing Meadows, New York City.

Daniil Medvedev won the men's singles title. Emma Raducanu won the women's singles title, becoming the first qualifier, male or female, to reach a major final and win a major title.

Dominic Thiem and Naomi Osaka were the men's and women's singles defending champions. However, Thiem withdrew from the tournament due to a wrist injury causing him to end his season early. Osaka lost in the third round to Leylah Fernandez.

Both Dylan Alcott and Diede de Groot achieved the Golden Slam in wheelchair quad singles and wheelchair women's singles, respectively, by winning all four majors and the Paralympics in 2021. Alfie Hewett and Gordon Reid also achieved the Grand Slam in wheelchair men's doubles by winning all four majors in 2021. Novak Djokovic was attempting to be the first man to complete a calendar Grand Slam in men's singles since Rod Laver in 1969, having won the men's singles tournaments at the 2021 Australian Open, French Open and Wimbledon, but unlike Alcott and de Groot, who also won the Olympic gold medal (Djokovic lost to Alexander Zverev in the semifinal for the gold medal match at the Olympics in 2021), he lost to Medvedev in the final.

This was the first Major tournament since the 1997 Australian Open not to feature Roger Federer, Rafael Nadal, Serena Williams, or Venus Williams in the main singles draw.

The United States Tennis Association allowed the return of spectators after the 2020 tournament was held behind closed doors due to the COVID-19 pandemic in New York. Due to a surge in COVID-19 cases resulting from the delta variant of the virus, spectators had to present a negative COVID-19 test or proof of vaccination in order to be allowed to enter the grounds.