The 35-year-old overnight leader shot a closing one-over 73 at coastal Torrey Pines to finish at eight under and land his first win since 2021.
Playing six groups ahead, Stevens began the day six shots off the lead, but surged into contention with a 68 as he chased a maiden victory.
His impressive number didn't rattle English, who made two early bogeys but steadied and calmly finished with 12 consecutive pars in chilly temperatures as a strong wind blew across the South Course.
Harris English held his nerve to triumph in tough conditions. (AP PHOTO)
"Doesn't have to look pretty," he said. "But I just had to get the job done."
"I knew it was going to be a tough day today, but I love that.
"I love this golf course when it plays really tough. I knew with the wind, you're probably not going to get somebody … coming up and throwing a 65, 66 out here today.
"So as a leader coming into the final round, you kind of like that. It's going to be a grind, and you're going to miss fairways, miss greens, but you've got to miss them in the right spot."
Andrew Novak was third at six under, missing out on his first tour victory with a disappointing 74 after briefly taking the lead.
Sungjae Im (71) and Kris Ventura (71) tied for fourth at five under.
A two-time winner of the tournament, former world No.1 Jason Day was among those to struggle as he posted a four-over 76, including five bogeys, falling from tied 15th overnight to finish tied 32nd at one over.
Jason Day slipped back in the final round. (AP PHOTO)
Fellow Australian Aaron Baddeley finished on the same score as Day after a 75.
English hadn't won since surviving an eight-hole playoff with Kramer Hickok at the Travelers Championships in 2021.
However he still had nine top-10 finishes in the previous two seasons after missing five months in early 2022 while recovering from hip surgery.
He also had a strong history at Torrey Pines, where he lost a four-way playoff to Day in 2015 and then finished third at the US Open in 2021.
The wind that forced an 86-minute delay in the second round on Thursday returned in intermittent force early Saturday on the oceanside holes, although it calmed somewhat in the afternoon.
Stevens turned pro in 2018 and joined the tour in 2023. The Oklahoma State product matched his best previous result in his runner-up finish to Corey Connors at the Valero Texas Open in April 2023.
He charged up the leaderboard at Torrey Pines despite the wind, making four birdies on the front nine. Stevens even saved par on the 18th after putting his second shot in the water while trying to reach the green in two.
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