The 22-year-old, a former world amateur No 1, closed with a seven-under-par 65 at Torrey Pines to finish three shots clear of the field on 13-under-par.
Rahm made two eagles as he stormed home in 30, the second coming at the last, where he holed a 60-yard putt.
“It does a lot for me,” he said of the victory. “I get to the play the Players Championship, I am likely going to the Fed Ex Cup, I am going to the majors, it is amazing.”
The victory was made even more special as his dad was in California to watch him finish ahead of Charles Howell III and CT Pan as they shared second spot.
“My dad hasn’t really been here for anything, he was at home working, so to have him here right now is such a special moment, I am so happy,” added Rahm. “My mum isn’t here but she is probably at home crying.”
Former Scottish Open champion Justin Rose finished joint-fourth on nine-under and said of his performance: “It was another good week for me and I just want to keep this momentum up.”
Martin Laird, the sole Scot in the field, missed the 54-hole cut after following scores of 70 and 72 with a third-round 76.
Brittany Lincicome won the opening event of 2017 on the LPGA Tour after claiming a play-off victory in the Pure Silk-Bahamas LPGA Classic.
She beat fellow American Lexi Thompson with a birdie on the first extra hole after the pair had tied with 26-under-par 266 totals at Paradise Island.
It was Lincicome’s seventh career win on the LPGA Tour but first since the 2015 ANA Inspiration.
Mel Reid, who is coached by Kevin Craggs, finished joint-13th in her first outing on the circuit since graduating from the Qualifying School at the end of last year.
Former Walker Cup player Wallace Booth is celebrating a welcome first win in five years.
It came on the Algarve Pro Golf Tour, where the Comrie man beat Irishman and former Stirling University star Cormac Sharvin in a play-off to win the Penina Classic II.
The pair tied on nine-under-par after two rounds, having carded matching scores of 69 and 68.
The success saw Booth prevail in a play-off for the first time, having lost three previously in his career.
Six Scots, including two-timer winner Stephen Gallacher, are set to join Tiger Woods in this week’s Omega Dubai Desert Classic.
David Drysdale, Richie Ramsay, Marc Warren, Scott Jamieson and Paul Lawrie are also definite starters at the Emirates Golf Club in the UAE on Thursday.
Drysdale has made the best start to the 2017 European Tour campaign among the Scots, having made five straight cuts to sit 30th in the Race to Dubai.
Duncan Stewart’s hopes of getting into the last event on the Middle East Swing look slim, sitting seventh on the reserve list first thing this morning.
Two Scots - Kenny Hutton and Fraser Mann - have made it through to the final stage in this season’s European Senior Tour Qualifying School in Portugal.
The duo progressed to the card shoot-out, which starts today, from a first-stage event
held at Silves Golf, part of the Pestana Resort.
Hutton, the former Downfield pro, finished joint-12th on five-over (74-71), seven shots behind Steve Cipa as the Englishman carded scores of 73 and 65 to claim top spot.
Mann, who spent a big part of his PGA career at Musselburgh, just made it through on eight-over (76-72) as 27 players in total progressed from that venue.
The other qualifier, held at Gramacho and also won by an Englishman in Jonathan Cheetham, saw Alan Saddington finish as leading Scot as he came up a shot short on 12-over.
Phil Helsby and Robert Hunter also missed out there on 19-over and 26-over but the qualifiers included Warren Bladon, the Englishman who won the Amateur Championship at Turnberry in 1996.
Offering cards to the top five, the 72-hole final is being held on the Pinta Course at Pestana Golf Resort.
Amateur duo Mark Anderson (Leven Thistle) and Scott Graham (Arbroath) shared top spot in the first Midland Golfers’ Alliance event of 2017 at a cold and windy Arbroath Links.
The two scratch players carded matching two-over-par 72s to finish a shot ahead of Lundin’s John Baxter, who won the handicap section with his net 69.