The former world number one will play all eight events of the fledgling $255m (£200m) series, which starts on Thursday at Centurion Club near London.
Johnson, 37, joined the PGA Tour in 2007 and has won $74m in his career.
“I don’t want to play for the rest of my life, this gives me an opportunity to do what I want to do,” he said.
In quitting the PGA Tour, the 2020 Masters champion – who is reportedly receiving $150m in appearance fees to play in the series – is giving up his opportunity to feature in the Ryder Cup.
He has been on the winning side in two of his five appearances in the biennial competition against Europe, including winning all five of his matches in last year’s record victory at Whistling Straits in Michigan.
“The Ryder Cup is unbelievable and has meant a lot to me, but ultimately I decided this was best for me and my family,” he said.
“All things are subject to change and hopefully at some point it will change and I will get a chance to do that again.”
PGA of America chief executive Seth Waugh said last year: “If someone wants to play on a Ryder Cup for the US, they’re going to need to be a member of the PGA of America, and they get that membership through being a member of the (PGA) Tour.”
Johnson’s decision represents a significant u-turn by the 2016 US Open champion, who said in February he was committed to the PGA Tour.
When asked what had changed in such a short space of time, he simply replied: “I thought it was best for me and my family. I resign my membership of the PGA Tour.
“What the consequences are going to be I can’t comment on how the Tour’s going to handle it. I can’t answer for the majors but hopefully they’re going to allow us to play.
“Obviously I’m exempt for the majors so I plan on playing there unless I hear otherwise.”
The majors are not run by the PGA Tour and Johnson’s victory two years ago in the Masters gives him a lifetime exemption for the tournament at Augusta National. His 2016 US Open triumph guaranteed him a spot in his national championship for 10 years. His Masters win also gives him a five-year exemption for The Open and US PGA Championship.
The Open Championship and US Open, which starts on 16 June at Brookline, Massachusetts, would have to introduce a special clause to disinvite any players competing in the LIV Golf events.
Six-time major champion Phil Mickelson will also compete in what will be his first appearance following a four-month break from the game.
The American has not played since controversial comments about the Saudi-funded events were published by his biographer in February. He is expected to talk to the media on Wednesday.
It has also been reported Spain’s Sergio Garcia and South Africans Louis Oosthuizen, Charl Schwartzel and Branden Grace, who are also in the 48-man field for the event on the outskirts of London this week, have all resigned their membership of the American-based circuit.
However, Northern Ireland’s Graeme McDowell has not resigned his membership of the PGA Tour, saying he did not want to get in a “legal situation” with the organisation.
He last played in the Ryder Cup in 2014, four years after holing the winning putt at Celtic Manor. He was a vice-captain in the victorious team in Paris in 2018 and again on the losing side last year.
The 42-year-old Northern Irishman, who won the US Open in 2010, has been touted as a potential captain of the European side when the event is played at Adare Manor in the Republic of Ireland in 2027.