Johnson leapfrogged both Rory McIlroy and Jason Day with his five-shot win at the Genesis Open, reaching the top spot in the Official World Golf Ranking for the first time in his career. He becomes the 20th different player to hold the No. 1 ranking since the OWGR was created in 1986.
Johnson's latest win was his fifth during the two-year window used to compile the rankings, and it caps a remarkable run of consistency that has seen him rack up 30 top-10 finishes in his last 50 OWGR starts.
Day's run at the top ended after 47 weeks, as he now drops back to No. 2 for the first time since his win at the WGC-Dell Match Play Championship. McIlroy, who has been idle for over a month while recovering from a rib injury, dropped to No. 3.
Thomas Pieters was a distant second to Johnson in Los Angeles, but the result still helped the Belgian jump 14 spots to No. 33 in the latest rankings. By remaining inside the top 50 this week, Pieters also qualified for next month's WGC-Mexico Championship.
Other moves from Riviera included Kevin Na, who jumped from 53rd to 44th with his T-4 finish, and Wesley Bryan, who finished alongside Na and is now inside the OWGR top 100 for the first time at No. 96. Scott Brown, who tied for second with Pieters, went from No. 231 to No. 114.
Henrik Stenson remains at No. 4 behind McIlroy, followed by Hideki Matsuyama, Jordan Spieth, Adam Scott, Justin Thomas and Sergio Garcia. Sweden's Alex Noren cracked the top 10 once again, slipping past Patrick Reed at No. 10 despite a missed cut in Perth.
Tiger Woods, who did not compete at Riviera because of a back injury, is now No. 704.