RANCHO MIRAGE, Calif. >> So Yeon Ryu won the ANA Inspiration today in a one-hole playoff with Lexi Thompson, who was given a four-stroke penalty late in the final round for an incorrect ball placement a day earlier.

Ryu birdied the 18th hole in the playoff to win her second major title, but her celebration was muted because of the bizarre circumstances on the Dinah Shore Course.

The 22-year-old Thompson had a three-shot lead and appeared to be cruising to her second major championship when LPGA Tour rules officials informed her of the penalty with six holes to play.

An email from a television viewer during Sunday’s final round alerted officials to the violation committed Saturday, and the LPGA Tour confirmed it with video review. Thompson had marked a 1-foot putt with a coin on the 17th green during her third round Saturday, but she replaced the ball perhaps 1 inch out of position.

“It’s unfortunate what happened,” Thompson said. “I did not mean that at all. I didn’t realize I did that. I felt strong through the finish, and it was great to see the fans behind me.”

Thompson’s composure was visibly shaken when the ruling dropped her one shot off the lead, but she incredibly birdied the 13th hole. She battled back into a five-way tie for the lead, making three birdies and a bogey on the final six holes of regulation at Mission Hills Country Club.

Ryu birdied the 18th hole to move in front, but Thompson crushed her approach shot on the 18th several minutes later. With emotions visible on her face amid loud chants of her name, Thompson gathered herself — but left a 15-foot winning eagle putt about an inch short.

Ryu, who also won the 2011 U.S. Women’s Open, claimed her second major title with an excellent playoff hole after her final-round 68 at the LPGA Tour’s first major of the year.

“I just cannot believe the situation,” Ryu said. “I didn’t even check the leaderboard. I thought Lexi played really, really well. I didn’t expect what happened to Lexi. It’s a very unfortunate situation. I didn’t expect it. I thought I’m well behind, so all I wanted to do was play my game.”

Ryu still made the traditional joyous leap into Poppie’s Pond with her caddie and family.

Norway’s Suzann Pettersen barely missed a birdie putt on the 18th to force a three-way playoff. She finished tied for third with Inbee Park and Minjee Lee at 13 under. Honolulu’s Michelle Wie shot a 69 to finish sixth at 11 under. It’s her second top-10 finish of the season.

But this event will be remembered for the extraordinary sight of LPGA rules official Sue Witters regretfully explaining the penalty to Thompson while she walked to the 13th tee.

“I can’t go to bed tonight knowing I let a rule slide,” Witters said. “It’s a hard thing to do, and it made me sick, to be honest with you.”

Thompson was penalized two strokes for an incorrect ball placement and two strokes for an incorrect scorecard.

“Is this a joke?” Thompson asked Witters.

After being assured it wasn’t, she responded: “This is ridiculous.”

Thompson choked up slightly, but gathered herself and mashed a drive.

While Park birdied the 16th moments later to create a five-person tie for the lead, Dinah Shore Course officials laboriously changed every number next to Thompson’s name on the scoreboard across from Poppie’s Pond.

Golf fans on the course and the Internet erupted with outrage when the LPGA’s decision became understood. Tiger Woods immediately came to Thompson’s defense on Twitter.

“Viewers at home should not be officials wearing stripes,” Woods wrote. “Let’s go Lexi, win this thing anyway.”

As awkward as the situation was, it could have been worse: If golf officials hadn’t made a rule change last year, Thompson would have been disqualified entirely.

The decision against Thompson was the second debatable penalty to hit a major leader in golf in the past year.

At the men’s U.S. Open at Oakmont last year, Dustin Johnson won despite playing the last seven holes without knowing his score. His ball had moved slightly while he lined up a putt on the fifth green, the USGA eventually hit him with a one-shot penalty after his round.