Suzann Pettersen set a course record by shooting a 9-under 63 in the first round of the LPGA's KEB HanaBank Championship on Friday.
The Norwegian finished a shot clear of Sweden's Karin Sjodin at the Ocean Course in Incheon, with five players tied for third, two shots back.
Ai Miyamoto of Japan, Spain's Azahara Munoz and the South Korean trio of Ryu So-yeon, Moon Hyun-hee and Kim Ha-neul all carded rounds of 66.
In perfect conditions at the course 40 kilometers (25 miles) west of Seoul, Pettersen sank five birdies in the first six holes to make a brilliant start to the three-day event.
Defending champion and world number one Yani Tseng had a 68.