The 37-year-old American, seeded 11, eased past over-matched Barbora Strycova of the Czech Republic 6-1, 6-2 in the semi-finals.
She will face Simona Halep for the title on Saturday after the seventh seed became the first Romanian woman to reach the Wimbledon final with a 6-1, 6-3 victory over Elina Svitolina.
Williams has a 9-1 career lead over Halep.
