Mr Clegg, whose appeal to younger voters was critically damaged when he broke a promise not to raise student tuition fees, lost his own seat in Britain's parliament in an election past year.
Clegg - who led the Liberal Democrats into coalition with the Conservative Party in 2010 - will move to Silicon Valley in January to succeed Elliot Schrage, the Financial Times reports.
"Throughout my public life I have relished grappling with hard and controversial issues and seeking to communicate them to others", Clegg said in a Facebook post. "I hope I will be able to play a role in helping to navigate that journey". Members of the European Union parliament have called for an audit of Facebook, and careful scrutiny based on competition laws.
"I'm not especially bedazzled by Facebook", he said in an article in the London Evening Standard in 2016.
He will start work on Monday and will spend a week at the company's Menlo Park headquarters, before moving to California permanently in the new year.
Facebook is also facing the threat of increased government regulation - including from Europe, where Mr Clegg served as a commissioner - and in recent months, several executives have left the company.
Schrage announced his departure from Facebook in June. He is set to remain present at Facebook as an adviser to Clegg and the rest of the leadership team over the coming years.