Yes, Elon Musk was one of the founders of OpenAI together with Sam Altman, Ilya Sutskever, Greg Brockman, Wojciech Zaremba & John Schulman.
However, he stepped down from company management in 2019 over conflicts of interest. OpenAI is an AI research organization made up of its for-profit business OpenAI LP and its primary corporation, OpenAI inc.