Jan Koum said he will be "taking some time off to do things I enjoy outside of technology."
The co-founder of WhatsApp, a messaging service owned by Facebook Inc with more than one billion daily users, said on Monday he was leaving the company, in a loss of one of the strongest advocates for privacy inside Facebook.
Jan Koum's plan to exit comes after clashing with the parent company over WhatsApp's strategy and Facebook's attempts to use its personal data and weaken its encryption, numerour reports suggest.
"It's been almost a decade since Brian and I started WhatsApp, and it's been an amazing journey with some of the best people," Koum, WhatsApp's chief executive, said in a post on his Facebook page referring to co-founder Brian Acton.
"But it is time for me to move on." He did not give a date for his departure and could not immediately be reached for comment.
Acton left the messaging service company in September to start a foundation, after spending eight years with WhatsApp.
Facebook Chief Executive Mark Zuckerberg commented on Koum's post, saying he was grateful for what Koum taught him about encryption "and its ability to take power from centralized systems and put it back in people's hands. Those values will always be at the heart of WhatsApp."
Facebook has battled European regulators over a plan to use WhatsApp user data, including phone numbers, to develop products and target ads. The plan is suspended, but WhatsApp said last week it still wanted to move forward eventually.
Stanford alumnus Acton and Ukrainian immigrant Koum co-founded WhatsApp in 2009. Facebook bought WhatsApp in 2014 for 19 billion dollars in cash and stock.