Johnson, who is looking for his second major win after taking down the 2016 U.S. Open, shot a five-under 65 to vault into first. He's one shot ahead of Scottie Scheffler and Cameron Champ and two shots in front of Collin Morikawa, Brooks Koepka and Paul Casey.
A group of talented golfers sits at six under, led by major winners Jason Day and Justin Rose.
Twenty golfers will enter Sunday at four under or better.
Here's a look at the top 20 and ties followed by some highlights and notes from Saturday's action.
1. Dustin Johnson: -9
2. Scottie Scheffler: -8
2. Cameron Champ: -8
4. Collin Morikawa: -7
4. Paul Casey: -7
4. Brooks Koepka: -7
7. Bryson DeChambeau: -6
7. Tony Finau: -6
7. Justin Rose: -6
7. Jason Day: -6
7. Daniel Berger: -6
7. Tommy Fleetwood: -6
13. Joel Dahmen: -5
13. Si Woo Kim: -5
13. Matthew Wolff: -5
13. Xander Schauffele: -5
13. Haotong Li: -5
18. Hideki Matsuyama: -4
18. Bernd Wiesberger: -4
18. Mike Lorenzo-Vera: -4
Scoreboard via PGA.com.
Highlights and Notes
The most impressive part of Johnson's day wasn't any one of his eight birdies in particular or the fact that he jumped over a loaded field to take the lead into Sunday.
Rather, it was how he responded after double-bogeying No. 9. He gamely shook that one off and proceeded to go four under on the back nine to take the lead.
He spoke afterward about his mindset following the double bogey, per Lukas Weese of The Hockey News:
Lukas Weese @Weesesports
I asked likely 54-hole leader at the @PGAChampionship Dustin Johnson about his thoughts walking to the 10th tee after a double-bogey on 9, given how difficult the back stretch of holes has been at TPC Harding Park. Below is his response: #PGAChamp #PGAChampionship https://t.co/0JFZHC2Euj
Johnson's putter proved to be the primary cause for his jump up the leaderboard after trailing second-round leader Haotong Li by four strokes heading into Saturday:
That putt on No. 17 put Johnson in the co-lead at the time, and he took the solo lead before the round ended.
Johnson has traversed through a roller-coaster season following the PGA Tour's restart after a three-month suspension because of the COVID-19 pandemic.
He missed the cut at the Charles Schwab Challenge, which was the first post-restart tournament, but he responded two weeks later with a win at the Travelers Championship at 19 under.
Three weeks later, however, Johnson shot 80 in each of his two rounds before getting cut at 16 over, which seemed inexplicable for a golfer of his caliber. Johnson then carded a 78 at the 3M Open the following week before withdrawing with a back injury.
But DJ rebounded at the WGC FedEx St. Jude Invitational with a 12th-place finish at eight under before cruising through the first three rounds of the PGA Championship. He's been on quite the ride this year, but Johnson could end up lifting the Wanamaker Trophy after finishing two shots short of Koepka for second the year before.
He'll be in the final group with Scheffler, who tore up the front nine with five birdies to vault into major championship contention. That effort included this birdie shot from the greenside bunker on the par-three eighth hole:
Scheffler had a mostly positive (and volatile) round that included eight birdies and three bogeys. After shooting four under on the front nine, the 24-year-old had just one bogey and four pars from No. 10 through No. 14.
But Scheffler caught fire to take the lead with three straight birdies, including this putt on No. 17:
Scheffler bogeyed the last, but he's just one shot behind Johnson as he looks for his first major win.
Elsewhere, Paul Casey looks primed for his 10th career top-10 major finish at seven under, and he's not out of the question to contend for his first-ever major win. Like Johnson, his putting took him far Saturday, including this birdie on the ninth to give him the co-lead at seven under:
Casey didn't finish with the co-lead, but he's in the mix. The same goes for Koepka, who is once again lurking at a major. He's won four of them, including two U.S. Opens and two PGA Championships.
He found himself at seven under and two back of Johnson with a birdie on the last hole, putting himself in better position to earn the PGA Championship three-peat, which hasn't been done since the tournament moved to a stroke-play format in 1958. Walter Hagen won four in a row from 1924 to 1927.
The group at six under includes Bryson DeChambeau, who drilled a 95-foot birdie putt for one of the tournament's top shots thus far:
ESPN will carry television coverage of the PGA Championship from noon ET to 3 p.m. Sunday. CBS will then pick up the tournament until its completion.