Inbee Park holed a four-foot putt on the first play-off hole to win the NW Arkansas Championship in Rogers.
The world No 1's birdie four at the only extra hole was enough to see off her Korean compatriot So Yeon Ryu.
Park had closed with a four-under-par 67 that included three straight birdies on the front nine, along with a solitary bogey at 11 followed by further birdies at 14 and 18.
Ryu meanwhile, who teed-off on Sunday as co-leader, closed with a 69 which yielded birdies at both 17 and 18.
However, the double-bogey six she posted at 13 proved to be her downfall.
In the play-off, Park chipped to within four feet of the flag with her third shot from just off the green at the par-five 18th.
Ryu's attempt to extend overtime failed when her birdie attempt with a wedge - from just off the back of the green - came up short.
Park heads to next week's US Open with five wins already in the bag this season, including the first two Majors of the year.
Park said: "Everything's going really well. I'm hitting the ball well and putting amazingly. Everything in my game is really coming together."