Johnson pockets the $18 million first prize after collecting five top-10 finishes in the opening six events of the breakaway series.
The 38-year-old finished 16th at the recent in Bangkok, which ended on Sunday, and collected enough points in the individual standings to be crowned champion despite one event of the season still remaining.
South Africa's Branden Grace currently lies second in the individual standings, 42 points behind the former world number one.
"Locking up the individual competition is big," said Johnson. "It's an honour to be LIV's first individual season champion."
LIV Golf CEO Greg Norman said: "The first chapter of LIV Golf's history could not be written without Dustin Johnson's name.
"By any measure, DJ is among the elite players in the world. From the start, he's been a LIV Golf cornerstone. He has more than lived up to his billing and he deserves immense credit for clinching LIV's first individual season title."
Johnson's financial windfall has not come without a cost, however. The American has been banned from the PGA Tour and ruled out of Ryder Cup eligibility along with all the other players who have chosen to join the breakaway tour.
The players also do not currently earn any world rankings points for their performances on the tour, and as a result, many of them have plummeted down the world rankings.
Norman recently urged golf's traditional powers to "grow up" and stop trying to block LIV Golf from being granted rankings points.
"There are 22 tours out there, I believe, that have world ranking points," Norman said during an interview with India's World Is One News during last week's LIV event in Bangkok.
"There is only one that is equal or a little bit superior to what LIV is. So it doesn't make sense from a Majors perspective, it doesn't make sense from a broadcaster's perspective. You are paying and investing for your strength of field and not allowing LIV players to get OWGR points is not doing the game of golf any good.
"Rise above it all, it's good for the players, it's good for the game of golf, it's good for production, it's good for corporations, it's good for fans, it's good for everybody.
"Just because you have a negative viewpoint and you're one of the voting members of an independent organisation, that you hate LIV and you're going to vote against it ... grow up."