Jack Dorsey is expected to step down as the boss of social media giant Twitter.
The 45-year-old is currently both the chief executive of Twitter, which he co-founded in 2006, and his payment business Square.
Shares in the social media platform company rose more than 10% after CNBC reported the chief executive is set to step down.
Mr Dorsey previously left Twitter in 2008, before rejoining in 2011 and then becoming chief executive for the second time in 2015.
Shortly before 4pm on Monday the American tech-magnate posted an explanation for his departure on Twitter.
"I want you to know that this is my decision and I own it," he wrote.
"It is a tough one for me, of course. I love this service and company....and all of you so much.
"I'm really sad, yet really happy. There aren't many companies that get to this level.
"And there aren't many founders that choose their company over their own ego. I know we'll prove this is the right move."
Parag Agrawal, the company’s chief technology officer, will take over the helm.
Mr Dorsey added: “I’ve decided to leave Twitter because I believe the company is ready to move on from its founders.
“My trust in Parag as Twitter’s CEO is deep. His work over the past 10 years has been transformational. I’m deeply grateful for his skill, heart, and soul. It’s his time to lead."
He has recently come under pressure from Paul Singer, the billionaire founder of hedge fund Elliott, to step down as the company's chief executive.
Last year Elliott and Mr Singer said that Mr Dorsey should not be chief executive of both Square and Twitter, before reaching a deal with the technology firm.
The social media giant, along with the wider sector, has also faced continuing scrutiny over its moderation of harmful content online, including how it handles misinformation as well as racist and other abusive posts.
Many campaigners have called for more regulation of the sector and greater accountability of senior managers at internet companies.
Mr Dorsey last tweeted on Sunday, saying simply: "I love Twitter."
