Davey, who has been acting leader since the 2019 general election, was a cabinet minister in the 2010-2015 coalition government, and beat his rival, Layla Moran, by 42,756 votes to 24,564.
The result was announced by livestream..
He will be the party’s fourth leader in five years, and has stressed his ministerial experience and commitment to tackling climate change during a drawn-out campaign.
The contest was initially shelved for a year as a result of the pandemic, before being rescheduled for the summer.
Davey’s predecessor Jo Swinson swelled the parliamentary party with defections from Labour. She fought the 2019 general election claiming to be a potential prime minister, but ended the campaign with just 11 MPs, losing her own seat to the SNP in the process.
Moran, 37, was a teacher before entering parliament in 2016. She is currently the Lib Dem education spokesperson, and had been expected to shift the party to the left if she won.