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.
Serena previously stated she was going to "evolve" from tennis following this year's U.S. Open ... and considering her success with her family and business ventures, it's clear she's not going to stop winning any time soon.