Williams guided Savezar to a thrilling win in the $40,000 feature at the Waikouaiti Racing Club’s annual meeting at Wingatui.
It was a third Waikouaiti Cup victory and an 800th win for Williams, the most successful southern female rider in racing history.
Savezar sat third for much of the 2200m race behind pace-setter Firoden.
The 5yr-old Savabeel mare then appeared to be in an awkward inner position on the home straight before Williams found some clear air and her ride found a wonderful kick to pip Firoden and El Gladiador at the post.
It was a second win from three starts for the Robert Dennis-trained Savezar, and a third win in seven races this season.
Williams had earlier claimed her 799th career win aboard Terri Rae-trained gelding Rockland.
Riccarton trainers Michael and Matthew Pitman combined with apprentice jockey Kavish Chowdhoory to get three wins at the Waikouaiti meeting.
Their third of the day was with Seikrid in the first of two races, a rating 65, in the Otago Daily Times Southern Mile series.
The Jamie Richards-trained Zouluminous won the other ODT Southern Mile race.
Namibia Miss posted another third in the mile series to be the overall leader after five heats on 14 points.
Wingatui trainers Brain and Shane Anderton enjoyed home conditions with two winners, a second and a third.
White Robe Lodge-bred and owned Carisbrook won a maiden over 1600m, and Ruby’s Lad pipped stablemate Burgie over 1200m.
That made it three wins and a second in four starts for Ruby’s Lad.
Wingatui trainer Terry Kennedy prepared Rays In Command for an impressive win in the open 1400m under the guidance of jockey Chris Johnson.
