At Number 31, Williams became the lowest-ranked women's winner in Wimbledon history.
Bartoli, who upset top-ranked Justine Henin to reach her first Grand Slam final, came back from 3-0 down in the first set but couldn't continue her surprising run.
In the men's draw, Roger Federer and Rafael Nadal will meet in another Grand Slam final. Federer reached his ninth consecutive major final by beating Richard Gasquet 7-5, 6-3, 6-4.
The rematch was guaranteed after Novak Djokovic withdrew in the third set.