Williams’s 6-3 6-3 victory over Caroline Wozniacki in the US Open final on Sunday took her level with Navratilova and Chris Evert on 18.
The figure had been a big target for the American and she admitted it had weighed heavily on her mind as she suffered early exits at the Australian Open, French Open and Wimbledon this year.
Navratilova and Evert joined Williams on court at Flushing Meadows to present her with a commemorative Tiffany bracelet marking the occasion.
“We all thought it was a matter of when, not if, after she won here last year,” said Navratilova.
“It took her the full year but I think now she doesn’t have to talk about it, she doesn’t have to think about it and she can just think about 22. That’s what she’s gunning for next. If anyone can get there (she can). She’s pretty young in tennis terms in that she hasn’t played as many matches as I had at this stage of my life.
“She’s pretty young and fresh, and if she stays motivated and healthy, the sky’s the limit.”
Williams turns 33 later this month and only Navratilova has won a women’s slam singles title at an older age in the Open era. But Williams is unquestionably the No 1 player in the world and shows no sign of slowing up yet.