Alex Jones, who said the Sandy Hook school shooting was a hoax, was allowed back on the X platform.

Elon Musk on Sunday allowed the right-wing provocateur and conspiracy theorist Alex Jones to return to the social media platform X, which barred him more than five years ago for posting harassing messages.

Mr. Jones spent years promoting the claim that the Sandy Hook Elementary School shooting in 2012 was a hoax. Last year, he was ordered to pay nearly $1.5 billion to the families of eight victims of the massacre for defamation.

Also barred by Facebook and YouTube, Mr. Jones had said he hoped Mr. Musk would reinstate his account on X, which was formerly known as Twitter.

In an interview with Tucker Carlson that was shown on X on Thursday, Mr. Jones said that users regularly called on Mr. Musk to bring him back to the platform.

“I trend all the time, ‘Hey, if you’re such an absolutist on free speech, bring back Alex Jones,’” Mr. Jones said.

“I understand that he needs to go through a process before he does that.”

On Saturday, Mr. Musk responded to a user on X who said it was time for him to bring Mr. Jones back to the platform. “Ok,” Mr. Musk wrote.

Mr. Musk then started a poll, asking his 165 million followers if he should bring back Mr. Jones’s account. By early Sunday, an overwhelming majority of the nearly two million respondents voted in favor of Mr. Jones’s being reinstated.

In the comments section of the poll, Mr. Musk signaled that he would do just that. “The people have spoken and so it shall be,” he wrote.

Mr. Musk restored the account on Sunday morning, although Mr. Jones did not immediately post.

The move to reactivate Mr. Jones’s account could further alienate advertisers, who have abandoned the platform in droves over concerns that Mr. Musk’s lack of content moderation allowed their brands to appear alongside offensive content.

At The New York Times’s DealBook Summit in November, Mr. Musk insulted advertisers using an expletive and told them not to spend on his platform.

Since then, X has pursued small businesses and sought their advertising dollars to replace the revenue it once counted on from major brands.