Twitter says it has permanently suspended the accounts of Alex Jones and his Infowars website.
It made the move after a number of tweets that violated Twitter's abusive behaviour policy, the company said.
A number of tech giants, including YouTube and Facebook, deleted the right-wing conspiracy theorist's content last month, citing hate speech.
The radio host is best known for spreading unsubstantiated allegations about tragic events, including 9/11.
He is currently being sued for defamation by the parents of two children killed in the 2012 Sandy Hook Elementary School shooting, which he has repeatedly claimed was a "giant hoax". Twenty children under the age of seven and six adults died in the attack.
Twitter said the ban was a result of "new reports of tweets and videos posted yesterday that violate our abusive behaviour policy, in addition to the accounts' past violations".
It did not specify what the violations were.
It added that it does "not typically comment on enforcement actions... against individual accounts", but was "open about this action given the broad interest in this case".
Mr Jones has accused media platforms of unfair censorship of his accounts.
Twitter had come under criticism last month when it refused to ban InfoWars and Alex Jones from its platform, despite YouTube, Facebook, Apple and Spotify deleting his content.
Twitter CEO Jack Dorsey said at the time this was because the accounts had not violated the platform's rules - but he vowed to suspend them if they ever did so.
What had Jones said on Twitter?
Mr Jones mostly uses his Twitter account to share content and videos from InfoWars with his 850,000 followers, and promotes conspiracy theories against liberals, Muslims and migrants.
- In July, he said that Democrats planned to launch a civil war on 4 July or US Independence Day
- Last year, he tweeted that Muslims in England were demanding that the Queen either convert to Islam or leave the country. However, the CNN clip Infowars based its article on dates back to 2009 and features a group led by radical preacher Anjem Choudary, who by 2017 was already serving a five-and-a-half-year sentence for inviting support for the Islamic State group (IS)
- He has previously said that "transgenderism" is a CIA "plan to depopulate humanity" and that the "normalization of mental illness" is an "evil paedophile plot to sexualize and destroy children"
- In 2013, he described then-President Barack Obama as the "global head of al-Qaeda", and later accused him of arming IS
On Wednesday, Mr Dorsey and Facebook's chief operating officer Sheryl Sandberg answered questions at a Senate Intelligence Committee hearing about what technology giants are doing to prevent future election meddling.
During the hearing, Mr Dorsey was also asked whether Twitter censors conservative voices.
Several Republicans, including US President Donald Trump, have accused Twitter of bias, which the company denies.
Mr Dorsey said his company did "not use political ideology to make any decisions", but admitted the company's algorithms had not always been "impartial".
Mr Jones also sat in on the hearing, and made headlines after he confronted Republican Senator Marco Rubio while Mr Rubio was being interviewed.
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