The winner of their final at Wimbledon on Saturday can claim that accolade, which entails extra prestige rather than just prize money or ranking points. Both champions have won all four Grand Slam titles during their careers, but Olympic gold in singles has eluded them.
"Whether I win or lose, that's not the big deal," said Williams, who defeated world No. 1 Victoria Azarenka of Belarus 6-1, 6-2 on Friday. "The big deal for me, USA is guaranteed another medal. I'm guaranteed to just go out there tomorrow and have fun. That's all I can do."
Roger Federer, who has won 17 majors, also has a chance at a career Golden Slam when he plays for the gold against Andy Murray on Sunday. He beat Juan Martin del Potro in the longest best-of-three set match of the Open era, at 4 hours, 26 minutes, while Murray ousted Novak Djokovic.
"Roger, me and Maria. The odds are good," Williams said about the opportunities to get a career Golden Slam. Andre Agassi and Rafael Nadal, who withdrew from the London Olympics because of a knee injury, won all four Grand Slam titles as well as Olympic gold in different years.
In 1988, Steffi Graf won a Grand Slam — all four titles in the same calendar year — as well as a gold medal at the Seoul Olympics, which reinstated tennis as a sport in those games for the first time in 64 years.
Williams said she felt no pressure or sense that she had to achieve anything else in an extraordinary career in which she first rose to the top of the rankings a decade ago.
"I don't feel like I'm missing anything. I feel like if I were to retire last week, I would be fine," she said.
Williams and sister Venus already have two gold medals in doubles, winning in Sydney in 2000 and Beijing in 2008, and are still in contention in the doubles this year. Serena has won 14 Grand Slam singles titles, the most of any active woman; Sharapova has won four majors, sinking to her knees and raising her arms skyward when she won the French Open this year.
The Olympic finalists have forged very different paths to their showdown on Centre Court at Wimbledon. Williams tore through a series of top players, including Azarenka, No. 8 Caroline Wozniacki and No. 14 Vera Zvonareva. She lost only 16 games in five rounds and has won 12 consecutive matches this summer at the All England Club, including her fifth Wimbledon title a month ago.
Sharapova has had tougher matches, including a three-set win over Sabine Lisicki, a German who beat her at Wimbledon. That loss cost her the top ranking, but Sharapova is playing some of her best tennis this year since a shoulder injury took her out of the game for an extended period several years ago and deprived her of the chance to compete at the Beijing games.
Williams is 8-2 in their head-to-head record, beating Sharapova most recently on clay in Madrid this year. In 2004, 17-year-old Sharapova defeated Williams at Wimbledon for her first Grand Slam title.
"Maria does everything really well," Williams said. "She's improved so much from week to week. I mean, the worst thing for her to do is lose because the next time she comes out, she wins and improves, she never looks back."
Sharapova defeated Russian teammate Maria Kirilenko 6-2, 6-3 on Friday, hitting a forehand drive volley past Kirilenko on match point. She's approaching the Williams match with grit.
"It doesn't really matter who is across the net," she said before learning she will play Williams.