The 25-year-old South Korean finished two shots clear of three players that included Stacy Lewis who had led the tournament after rounds one, two and three.
Yang, who had started the final round one shot adrift of Lewis, played the opening 10 holes in four-under-par to move top of the leaderboard.
Although she carded bogeys at 14 and 16, Yang had done enough to claim title No 2 ??? the first had arrived on home soil 16 months ago.
Lewis closed with a level-par 72, and was ultimately undone by a double-bogey six at 15.
The experienced American was joined in second place by Korean Mirim Lee and Yani Tseng of Taiwan who posted Sunday rounds of 69 and 67 respectively.
The day???s lowest round belonged to Beatriz Recari whose superb 63 included 11 birdies, as the Spaniard moved from 26th overnight to finish fifth and end up as the leading European.
Top Briton was Scotland???s Catriona Matthew whose 70 left her 10 shots behind Yang.