Elon Musk said he was about to make one of the most visible changes to Twitter since he took control of the social media company last fall: replacing its widely recognized bird logo.

In a tweet early Sunday morning Eastern time, Mr. Musk said that “soon we shall bid adieu to the twitter brand and, gradually, all the birds.”

He added shortly after, “If a good enough X logo is posted tonight,” it would “go live worldwide tomorrow.”

“X” is a term for what Mr. Musk has described as an “everything app” that could combine social media, instant messaging and payment services, akin to the popular Chinese app WeChat.

Mr. Musk has said that buying Twitter is “an accelerant to creating X,” and the corporate entity he created to purchase and control Twitter is called X Holdings.

Mr. Musk spoke on a Twitter audio livestream early Sunday to say he was changing Twitter’s logo. “It should have been done a long time ago,” he said. “Sorry it took so long.”

A few hours later, Mr. Musk said in an email to Twitter’s employees that “we are indeed changing to X” and that it was happening “today.” “This is my last message from a Twitter email,” he wrote, before signing off with a salute emoji.

Mr. Musk has few barriers to making such alterations at the company after taking it private as part of his acquisition of the firm. But he could still encounter resistance from the banks that have lent him billions of dollars and the private investors he brought into the deal, who could raise concerns about jettisoning one of Twitter’s most visible assets.

The company saw its advertising revenue plummet amid the departure of sales executives and worries that the site had become more prone to problematic content. It now faces a well-funded rival in Threads, the recently introduced Twitter-like service from Meta, the owner of Facebook.

Twitter did not immediately respond to a request for comment.

Mr. Musk has had a long affinity for the letter X. In 1999, he co-founded X.com, an online bank, and later merged it with another start-up to create PayPal. In 2017, he said that he repurchased the X.com domain from PayPal.

Mr. Musk has not always followed through on his public pronouncements, such as when he tweeted that the company would create a content moderation council to judge what kind of speech is acceptable on the site.

But he has pressed ahead in altering certain Twitter practices, like ending the free verification of prominent users’ accounts, denoted by a white-and-blue check mark, and charging users a subscription fee for the check mark instead.