Rahm's decision is likely to have huge repercussions for the ongoing negotiations over the future of men's professional golf.
The Spaniard said in 2022 that LIV's three-day events, with shotgun starts and no cut, was "not appealing" and he was chasing a golfing legacy over money.
His victories in this year's Masters and the 2021 US Open guarantee him exemptions to play in all four majors for several years, but this decision puts his Ryder Cup future in jeopardy. Europe's players must be members of the DP World Tour to be eligible to play in the biennial competition.
That rendered record points scorer Sergio Garcia, Lee Westwood and Ian Poulter ineligible after they resigned from the European tour in May in the wake of being fined and banned for their involvement with LIV.
Europe also switched captain midway through the two-year cycle after Henrik Stenson opted to join LIV, with Luke Donald taking over.
Rahm has signed his DP World Tour membership forms for 2024 and has said that he wants "to maintain my PGA Tour and DP World status".
Before the Ryder Cup, he was critical of LIV's European players not being allowed to compete.
American Brooks Koepka, who won his fifth major at the 2023 US PGA Championship, was the only LIV player competing in Rome.
"It's sad politics have got in the way of such a beautiful event," said Rahm earlier this year.
"It's the best Europeans against the best Americans, period, And whatever is going on, who is playing LIV and who is not playing LIV to me shouldn't matter."
Rahm won three points as Europe regained the trophy with a 16½-11½ victory over the United States in Rome in September.
Rumours of the Spaniard's move to LIV gathered pace after pulled out of Tiger Woods and Rory McIlroy's new TGL venture, saying it would "require a level of commitment I can't offer".
Rahm had been one of the first to commit Woods and McIlroy's high-tech indoor simulator league, which has been postponed until 2025 after its facility in Florida sustained damage.
He said his decision "wasn't anything personal" against the players on the PGA Tour and "hopes the best for the future" of the sport in a "moving and changing environment" which will eventually allow him to play across both formats.
"I found a great platform on the PGA Tour and I am forever grateful for the platform they have given me," he added.
"If I'm lucky and things go well in the future, I still want to be part of that platform.
"LIV Golf gives me the freedom to play golf when it doesn't conflict with the PGA Tour or DP World Tour and I certainly want to be part of that in the future."
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