Serena Williams Loses In Third Round Of U.S. Open, Final Match Of Career

Serena Williams -- the greatest woman to ever step foot on a tennis court -- has played the last match of her career ... after losing in the third round of the U.S. Open.

Friday's matchup was an epic thriller ... with her opponent, Ajla Tomljanović, taking the first set, 7-5, but Serena bouncing back in the second with a 7-6 (7-4) comeback.

Unfortunately for Williams, the magic ended there -- she fell 6-1 to Tomljanović in the third.

Serena was emotional in her final post-match interview ... tearing up as she thanked her parents for their leadership so early in her career.

Williams says she wouldn't be Serena "if there weren't Venus" ... giving a special tribute to her sister

The GOAT also thanked her fans ... saying, "It's been a fun ride. It's been the most incredible ride and journey I've ever been on in my life." Serena seemingly kept the door open on a return to the court ... saying it's possible she could compete again.

It was a monumental run for the 23 Grand Slam winner -- with celebs like Tiger Woods, Russell Wilson and Ciara, Spike Lee, Zendaya, Mike Tyson and more showing up for support.

Williams finishes her career with seven Australian Open victories and seven Wimbledon titles.

Serena also won the U.S. Open tourney six times ... and the French Open three times.

Williams has been the #1 ranked women's player for a large part of her career.

Williams is one of the the most influential tennis player to ever live ... and it was evident in the praise she received throughout her last dance.