Farron replaces former deputy prime minister Nick Clegg, who resigned after the party won only eight seats in May’s general election.
The MP for Westmorland and Lonsdale won 56.5% of the nearly 34,000 votes cast by party members to defeat former care minister Norman Lamb in the ballot.
On Twitter, Farron thanked members for their support and added: “This is a liberal country. Our job now is to turn millions of liberals throughout the UK into Liberal Democrats.”
He is expected to give his first speech as party leader later this evening.
