The 13-time Grand Slam champion advanced to her seventh Wimbledon final by beating second-seeded Victoria Azarenka of Belarus 6-3, 7-6 (6) Thursday.
Williams finished with a Wimbledon record 24 aces, and won 20 of the 24 points on her serve in the first set.
Williams will face Agnieszka Radwanska in Saturday's final. The third-seeded Pole beat Angelique Kerber 6-3, 6-4 in the other semifinal.
Radwanska trailed early in the first set, but won five straight games to close out the set and then took an early lead in the second.
The third-seeded Pole will face either four-time Wimbledon champion Serena Williams or second-seeded Victoria Azarenka in Saturday's final. Those two were playing next on Centre Court.
Radwanska is the first Polish woman to reach a major final since 1939, when Jadwiga Jedrzejowska lost in the French Championships.