Mr Clegg, 51, succeeds Elliot Schrage and will report to Ms Sandberg beginning on Monday.
Elsewhere in the article, Clegg called for a "new deal between the tech world and politics", saying that tech companies need to embrace new ways for people to control their personal data, and governments should "avoid a knee-jerk condemnation of the disruption and potency of new technologies". "After nearly 20 years in European and British politics, this is an exciting new adventure for me", Clegg wrote on his Facebook page.
The move came as a shock to much of the British political commentariat.
Clegg will be operating under vast pressure in his new role, as Facebook attempts to tackle the problem of fake news on its platform before United States mid-term political elections in November.
According to the Financial Times, who first reported the news, Zuckerberg himself had been headhunting Clegg for "months".
The former politician has pushed for a second referendum that could stop Brexit but the proposal has been ruled out by Prime Minister Theresa May.
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Clegg was a divisive figure while in coalition government with David Cameron's Tories, reneging on a host of Liberal Democrat manifesto pledges while in office. Sir Nick, a former European Commission trade negotiator, remains well-connected in Brussels, where regulators are taking a particular interest.
In a surprise defeat previous year, Clegg lost his seat in parliament in the U.K.'s general election.
Clegg has most recently been in the public eye as a high-profile campaigner for a second European Union referendum.
He will move to California with his family in the new year.