Joaquin Niemann held his nerve on a challenging final day to shoot a closing even-par 71 and complete a wire-to-wire win at The Genesis Invitational with a total of 19-under 265.
That was two in front of Cameron Young and a charging Collin Morikawa (65).
Adam Scott and Viktor Hovland shared fourth place a further three strokes back, while Justin Thomas was solo sixth on 13-under.
In a week of strange scoring, Niemann seemed to be playing a different course to virtually everyone else when opening with a pair of eight-under 63s.
And an eagle at the 10th in the third round took him to 21-under, a shot better than Lanny Wadkins' 37-year-old course record mark of 20-under.
With a healthy cushion and his nearest challenger rookie Young, Niemann didn't need any further fireworks and playing the rest of the tournament in two-over from that point proved enough.
After starting the day with a three-shot lead, that was reduced to one at the seventh when Niemann bogeyed and Young birdied.
But the leader responded with a bounceback birdie at 8 and then, decisively, chipped in for eagle at the 11th.
From there he could afford to drop shots at 14 and 15 and still get over the line with a little to spare after pars at the final three holes.
Morikawa, eight back at start of play, proved the biggest threat late on when the Open champion eagled the 10th and picked up further shots at 16 and 17.
A brilliant approach to 18 threatened to put further pressure on Niemann but he missed a nine-foot putt that would have put him within a shot.
That allowed Niemann to play the last with a two-shot lead and a par closed it out for the 23-year-old.
Niemann, who had the trophy presented to him by tournament host Tiger Woods, said: "The first two days I think it was a different tournament for me. Obviously I play my best golf on Thursday and Friday.
"I knew that the weekend was going to be hard, it was going to be a battle. I knew I had to be fighting myself a lot during those two days.
"It's the toughest tournament I think during the year. It's got the best field, the best players are here and that proves to myself that I can be competing with the top guys, I can be up there in the world ranking.
"I think it's going to give me a lot of confidence for what is coming next. I think at the beginning of the year, just started playing great golf at Torrey (tied sixth in the Farmers Insurance Open).
"Coming this week I was feeling really confident about my game and I was able to handle it during the week."
Runner-up Morikawa reflected: "I told (caddie) J.J. yesterday if I was within nine I thought I had a chance because you never know what's going to happen, you really don't.
"Game felt really good coming into the week especially after the couple of not changes but fixes and back to normal, and putting obviously was great.
"You know, I just had to put together a few better rounds and make a few less mistakes, but overall I'm happy with the way things kind of played out. Wish I had that putt on 18 again, but it is what it is."
Mixed outcomes on Riviera trends
The last six winners of The Genesis Invitational had all previously had a top five in the event, highlighting the importance of course form at Riviera.
With previous finishes at the L.A. track of 43rd, missed cut, 44th, Niemann broke that sequence.
However, if digging deeper it's worth noting that last year he'd opened 67, 68 to sit second at halfway so he did clearly get on with the course.
Looking at his path to victory, Niemann certainly backed up the idea that strong iron play was the key to success.
The Strokes Gained: Approach rank of the last five Genesis winners were 3rd, 20th, 11th, 6th and 3rd. Niemann finished 1st in that category after picking up over seven strokes on Approach.
As for the rest of his game, he was 1st SG: Tee To Green, 2nd SG: Around The Green, 17th Off The Tee and 26th for SG: Putting. In other words, solid in every aspect.
The top three finishers (Niemann, Young and Morikawa) were all in the top six for SG: Approach.
With the win, Niemann jumped to 20th in the Official World Golf Rankings, his highest ever position.
Fate of the big guns
Jon Rahm remains World No.1 but Morikawa has closed the gap at the top after the Spaniard had to settle for tied 21st at Riviera.
Rahm never featured on the leaderboard and was nearest at the finish after leaping 39 spots on Sunday when matching Morikawa's low round of the day, a 65.
As usual, Rahm drove it well (3rd Off The Tee) but his short game was poor (66th SG: Putting, 68th Around The Green) until the final round (4th and 16th in those two categories).
Local star and World No.4 Patrick Cantlay had to settle for tied 33rd - a full 14 shots behind the leader - after just one good round (Saturday 66) out of four while Dustin Johnson - perhaps distracted by all the Saudi talk - missed the cut after making the top 10 in seven of his previous eight Riviera starts.
World No.4 Viktor Hovland was six back after three rounds and got to within four before slipping back again.
Nevertheless, his fourth place added to a debut fifth at Riviera 12 months ago so this is clearly a good course for him.
Hovland now has a win (Dubai Desert Classic) and two fourths in his last four worldwide starts.
As for World No.5 Rory McIlroy, he was never up with the pace but rounds of 67-68 on the weekend secured tied 10th and a seventh straight top 15 finish which stretches back to August.
Rory putted well (6th SG: Putting) but his irons were modest (49th Approach).
He noted later: "I've never seen the greens this good at Riv. I've never holed as many putts here as I have this week."
Scottie Scheffler (tied seventh) and Justin Thomas (solo sixth) both had strong weeks to nudge up the rankings.
Last week's Phoenix winner Scheffler is up to sixth in the world while Thomas advanced to seventh.
Woods presents trophy but recovery still a long way off
It was heartening to see Tiger Woods well enough to present Niemann with the trophy on Sunday following last year's accident.
Woods gave an update earlier in the week, saying: "I can walk on a treadmill all day, that's easy, there's no bumps in the road. But walking on a golf course where there's undulations… I have a long way to go.
"My leg was not in a very good position about a year ago and I've had to work through a lot of different operations and a lot of different scenarios and it's been tough, but I've gotten here and I still have a long way to go."
While a full competitive return remains a long way off, Woods admitted he would be physically capable of playing the pre-tournament par-three contest ahead of the Masters on April 6.
"I can do that now," he added. "Whether I do that or not, I don't know.