Ko won the Swinging Skirts Ladies Masters in Taiwan by three strokes over a field that included four other Top 10 players.
It was the young New Zealand player's fifth win on a major tour but first since her petition to the LPGA to turn professional was accepted. She tied for 21st at the LPGA's CME Group Titleholders event in her first pro tournament.
Ryu So-yeon was second to Ko, who jumps past Ryu in the rankings, going from sixth to No. 4. Ryu holds onto the No. 5 spot and Feng Shanshan drops two places to sixth.
Inbee Park, who was third in Taiwan, remains the world No. 1-ranked women's golfer. She has held the top position for 35 weeks.
The women's world golf rankings Top 10, listing player's name, home country and rankings points average:
1. Inbee Park, South Korea, 11.47
2. Suzann Pettersen, Norway, 10.83
3. Stacy Lewis, United States, 9.61
4. Lydia Ko, New Zealand, 7.78
5. Ryu So-yeon, South Korea, 7.01
6. Feng Shanshan, China, 6.77
7. Choi Na-yeon, South Korea, 6.10
8. Karrie Webb, Australia, 5.43
9. Lexi Thompson, United States, 5.05
10. I.K. Kim, South Korea, 4.87
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Boston schools pull out free condoms over wrapping complaints