He also changed his Twitter profile to read "Chief Twit"
Many analysts argued the price Mr Musk is now paying for the company is too high given the decline in the values of many tech stocks and Twitter's struggle to attract users and grow.
On a recent earnings call, the Tesla founder said Twitter was "an asset that has just sort of languished for a long time, but has incredible potential, although obviously myself and the other investors are overpaying for Twitter right now".
Long road to a deal
Mr Musk's early investments in Twitter initially escaped public attention. In January, he began making regular purchases of shares, so that by the middle of March he had accumulated a 5% stake in the firm.
In April, he was revealed as Twitter's largest shareholder, and by the end of the month a deal was finally reached to buy the company for $44bn (£38bn).
He said he planned to clean up spam accounts and preserve the platform as a venue for free speech.
But by mid-May Mr Musk, a prolific Twitter user, had begun to change his mind about the purchase, citing concerns that the number of fake accounts on the platform was higher than Twitter claimed.
n July he said he longer wished to acquire the company. Twitter, however, argued the billionaire was legally committed to buying the company.
Twitter eventually filed a lawsuit to hold him to the deal.
In early October, Mr Musk revived his takeover plans for the company on the condition that legal proceedings were paused.
Mr Musk, a self-styled "free speech absolutist" has been critical of Twitter's moderation policies and the news will be greeted with mixed feelings by Twitter users and employees.
Some users, particularly those on the US right, argue conservative voices are censored on the platform - an accusation that Twitter denies.
Former US President Donald Trump remains banned from the platform - a decision Mr Musk has previously said was "foolish" and that he would reverse.
But others fear relaxing moderation policies would allow hate-speech to proliferate.
In a tweet addressed to Twitter advertisers Mr Musk said that the platform could not become a "free-for-all hellscape" and must be "warm and welcoming for all".
The entrepreneur has also posted that his plans for Twitter include "X, the app for everything".
Some suggest this might be something along the lines of the hugely successful Chinese app WeChat, a kind of "super app" that incorporates different services including messaging, social media, payments and food orders.