Putt for dough: Sei Young Kim's birdie on No. 18 wins CME Group Tour Championship, $1.5 million

Sei Young Kim was unaware she needed a birdie on No. 18 to take the $1.5 million winner's check, but she drained the 25-foot putt anyway. Sam Greenwood/Getty Images

NAPLES, Fla. -- A 25-foot putt was all that stood between Sei Young Kim and a $1.5 million paycheck.

After maintaining the lead for all four days of the CME Group Tour Championship, the 26-year-old South Korean saved the best for last. Hitting a 6-iron from the 18th fairway, Kim put herself in position to win with a 25-foot birdie putt.

At 17-under, Kim didn't realize the putt would determine whether or not she would walk away with the $1.5 million winner's check, the largest in women's golf history. She was focusing only on herself and the score of her playing partner, Nelly Korda. Kim thought she could two-putt and win. As a result, she hit the 25-feet putt like she would any other putt.

"I was only aware of Nelly's position when I was putting," Kim said after the final round. "So, I just thought of two-putting to secure my win. Coming into the 18th putt, I just reminded myself what I practiced out on the putting green. Just nice pace putt."

With barely any hesitation, Kim stood over her ball -- not even looking toward her longtime caddie Paul Fusco or asking for a line -- and hit the putt. The less-than-10-second-long putt felt like an eternity, almost rolling in slow motion, as spectators, volunteers and media members watched in silence.

As the ball inched closer to the cup, the silence permeated the gallery. Then Kim lifted her putter toward the sky, just moments before the ball began to drop into the cup. The crowd erupted. Just a few minutes after playing partner Caroline Masson finished putting (the last putt of the day), fellow LPGA players Amy Yang and Jin Young Ko ran onto the 18th green and started spraying their friend and competitor with water in celebration.

At that point, it became clear to Kim that she just won $1.5 million.

"I knew that when I heard the crowd and saw Amy and Jin Young running out, I knew that I won," Kim said. "Today, I focused on just maintain my score. I knew that if I could keep up with Nelly that I could win this tournament, so I did that."

That birdie sealed Kim's finish at 18-under 270 and solidified her No. 2 spot on the LPGA money list behind Jin Young Ko, who tied for 11th at the LPGA finale and previously this year won LPGA player of the year (with four victories, including two majors) and the Vare Trophy for the lowest scoring average.

Heading into the 18th hole, Korda remained at 15-under. The first to putt on the final green, Korda sunk her birdie putt and finished at 16-under. It wouldn't be until signing her scorecard that Kim would realize Korda wasn't the only one she should've been focusing on.

England's Charley Hull found herself in contention after making birdie on the final three holes. Finishing a group ahead of Kim, Hull had to wait to see whether she would take home the CME Group Tour Championship trophy for a second time in her career, face Kim in a playoff or finish second.

"I found out about Charley's [Hull] score when I was submitted my scorecard," Kim said. "I did not know. So, luckily I made the putt."

Hull's only victory on the LPGA Tour came in her second year, when she won the 2016 CME Group Tour Championship. And after finding herself atop the leaderboard with a standout 6-under third round at Tiburon Golf Club, Hull knew she had a chance to win in a familiar place.

"The winning memories are always in my mind around this golf course. I think I might've shot 5 or 6 under the last day when I won and shot 6 under today," Hull said. "My mindset was pretty much just the same as all week: just make birdies. Go out there and have fun, and I did."

About 15 minutes after Hull signed her 17-under scorecard, the final group of the day approached the 18th green. Kim made her birdie putt. And Hull knew it was all over.

"On the 15th hole, I thought, 'If I can make a birdie in, I've got a good chance.' I didn't birdie 15, but 16, 17, 18, so I was pretty happy," Hull said. "I feel pretty happy considering the first day after the first hole, I was 2-over par because I started with a seven. To finish 17 under, and I know just missed by one, but it was so close."

It wasn't just Hull who gave Kim a run for her money in the final round. American Danielle Kang birdied five of the first nine holes. Climbing up the leaderboard all day, Kang found herself at 14 under with only two holes to go. Then, on the par-5 17th, Kang made eagle. Just like that, Kang found herself only one shot behind Kim. Playing two groups ahead of Hull and three groups ahead of Kim, Kang's final birdie putt on No. 18 fell just inches short. Despite the missed birdie on the final hole, Kang still managed to go from a tie for ninth at the end of the third round to a tie for third on Sunday.

"[My] thought process was give everything I've got out there and see what happens," Kang said. "I just kept trying to make birdies. Putter kind of got cold after nine holes. I gave myself a lot of opportunities on the back nine, and they just didn't drop. But I had a really good attitude about it. It's never over until it's over, right?"

It wasn't over until the final minutes, when Kim made her dramatic birdie putt.

"It means a lot to me just knowing that I just won the biggest purse in women's golf history," Kim said. "That itself is an incredible honor."

The victory was Kim's 10th on the LPGA Tour, making her the fourth Korean player with at least 10 LPGA wins, joining: Se Ri Pak (25 wins), Inbee Park (19) and Jiyai Shin (11).

What's next for the $1.5 million prize winner and Korean golfer elite as she approaches her sixth LPGA season in 2020?

"I'm going to head back to Dallas, where I live, be there for a few days, and head to celebrate with my family over there [in Korea]," Kim said. "I'm going to come back to the States and do my winter training in Miami."

Her plans for that huge winner's check?

"I haven't really thought about, to be honest," Kim said. "It just happened, so I don't know. I wasn't really even thinking about it. I was just trying to play the best golf.

"I do want to do something meaningful, so I'm going to give it some thought. I'll go home and give it some thought. But, right now, I don't know."