Making the announcement in a series of tweets that evidenced his fondness for the company, Bain said: "After six years and a once-in-a-lifetime run, I have let Jack [Dorsey, the chief executive] know that I am ready to change gears and do something new outside the company."
Bain will be replaced as chief operating officer by chief financial officer Anthony Noto and will stay with the company for a few weeks to assist with the transition, according to a Twitter filing with the stock market.
The role covers global ad sales, data, ad server MoPub, global partnerships and business development. Noto will retain his previous responsibility for Twitter’s emerging live content business, which includes live streaming of Thursday night NFL American football games.
Twitter is searching for a new chief financial officer.
Bain worked at Rupert Murdoch’s News Corporation before joining Twitter in 2010. He quit as president of News Corp’s Fox Audience Network online sales outfit to take the role of president of global revenue with the then fledgling social network.
When Dorsey returned as chief executive last year, Bain was appointed to chief operating officer.