The deal could also help xAI's ability to train its chatbot known as Grok.
"xAI and X's futures are intertwined," Musk, who also heads automaker Tesla and SpaceX, wrote in a post on X.
"Today, we officially take the step to combine the data, models, compute, distribution and talent."
He said the combination values "xAI at $80 billion and X at $33 billion ($45B less $12B debt)".
Representatives for X and xAI did not immediately respond to requests for comment. Much of the deal's specifics remain unclear, such as how X's leaders would be integrated in the new firm or whether there would be regulatory scrutiny.
Musk, the world's wealthiest man, is also a close ally of United States President Donald Trump and heads the Department of Government Efficiency.
Saudi Arabian investor Prince Alwaleed bin Talal, who owns the investment company Kingdom Holding, said he had requested the development.
--Reuters--