It is official, and it is a landmark moment in the history of social media, as well as a puzzling new twist for a billionaire best known for rockets.
The stock price of the company on the day Musk started investing in it was less than it is now.
More than half of that amount will come from Musk's own pocket, with another $13 billion or so coming out of his shares in the company.
The future of the popular but battle-scorched site is anyone's guess.
Parag Agrawal, the CEO, said in the statement that they have a purpose and relevance that impacts the entire world.
It's not clear how that will play out, given Musk's history of shutting down critics.
Musk said in the announcement that free speech is the bedrock of a functioning democracy.
He said that he was looking forward to working with the company and the community of users to unlocked it.
I hope my worst critics stay on the site, because that is what free speech means.
The future of the company is uncertain as Musk's purchase could represent a shift in the company's business and cultural context.
The billionaire CEO has said that he doesn't care about economics at all, and that he isn't in it for the money.
Commentators are pointing out that Musk's vague plans may end up being against the First Amendment.
It's not the funniest part of the list, but it's one of the goals that work against each other.
It's up to Musk to follow through on his big goals, though, as always, whether he'll have any spare time or willpower in addition to his other ventures is anything but certain.
There is more on the purchase.