On Saturday, Williams will face first-time Olympian Maria Sharapova, who beat Russian teammate Maria Kirilenko 6-2, 6-3 in the semifinals.
Williams has lost only 16 games through five rounds and has won 12 consecutive matches this summer at the All England Club, including her fifth Wimbledon title a month ago.
She teamed with sister Venus to win the gold medal in doubles in 2000 and 2008. They had a chance to clinch at least a silver in a semifinal later in the day.
Williams has won 14 Grand Slam singles championships, the most of any active woman.