Williams, making her first appearance at the event since 2005, reached her seventh final in eight appearances at Stanford. She’s won two titles but none since 2002.

The eighth-seeded Bartoli, who lost in last year’s final, played a steady match against the second-seeded Williams and will likely move up two places into 12th when the next world rankings are released. Williams is expected to remain third.

Bartoli made an adjustment this season with her serve to get more power from her legs, and it helped keep Williams—who favors a strong baseline game—on her heels.

“I had a great tournament,” Williams told a record crowd of 3,852 after the match. “Marion was too good today (yesterday).”

Williams fell to 31-8 on the season, with four of those losses to top-15 players. She lost for just the third time in her last 15 matches, after winning 14 straight earlier this season.

Bartoli improved to 32-13 in winning for the seventh time in eight matches. She’s 3-4 against the top 10 this year.

Bartoli, who lost to Williams in the 2007 Wimbledon final in their only previous meeting, appeared calm as she landed two consecutive aces to win her second title of the year and the fifth of her career.

Bartoli won the match despite Williams recording 54 winners to her 18. Williams also had eight aces and committed 12 double faults.

Williams, who has not won an outdoor U.S. hardcourt tournament in seven years, looked like she was ready to make a rally after erasing a 4-2 deficit in the second set. But Bartoli broke on the first game of the third set and maintained her cool under the hot California sun.