The ex-Liberal Democrat leader, who lost his Sheffield seat at last year’s general election, is due to take up his post on Monday and will move to California with his family in the New Year.
The appointment comes as the social media giant faces criticism over the proliferation of “fake news”, the Cambridge Analytica data scandal and a mass security breach.
Facebook founder Mark Zuckerberg was personally involved in hiring Clegg, who is understood to be the most senior European politician to take up a senior executive role in Silicon Valley.
The move will be seen as part of the effort by the under-fire company to mend its badly tarnished reputation, by recruiting outsiders to its top team.
Clegg said Facebook and its apps, including Whatsapp and Instagram, were “at the heart of some of the most complex and difficult questions we face as a society”, over individual privacy, the integrity of the democratic process, the balance between free speech and prohibited content, concerns over artificial intelligence and protecting children.
He said: “I believe that Facebook must continue to play a role in finding answers to those questions – not by acting alone in Silicon Valley, but by working with people, organisations, governments and regulators around the world to ensure that technology is a force for good.”
He added: “I am looking forward to being part of this endeavour. Throughout my public life I have relished grappling with difficult and controversial issues and seeking to communicate them to others. I hope to use some of those skills in my new role.
“As someone who has spent a lifetime arguing for Britain’s wholehearted commitment to Europe, it is of course a wrench to be leaving the public debate at a crucial time in the Brexit process.
“But the key decisions will soon pass to Parliament, of which I am no longer a member, and once I had decided to take up this unique new challenge at Facebook, I felt it was best to get going sooner rather than later.”