Sir Ed Davey has won the race to become the new leader of the Liberal Democrats.
The acting leader will now take over on a permanent basis after beating his competitor, fellow MP Layla Moran.
Sir Ed secured 63.5% of the vote, compared to 36.5% for Ms Moran.
At an event in London, Sir Ed said it was time for the party to "wake up and smell the coffee" after only securing 12% of the vote in the last general election.
In an email to party members, he said he would launch a "national listening project" to help make the Lib Dems "relevant again", adding: "We won't be able to do this unless we show people we share their values and are on their side."
The result comes eight months after the Lib Dem's former leader, Jo Swinson, stepped down from the role after losing her seat in 2019 general election.
Ms Moran congratulated her opponent on Twitter, saying: "I look forward to working with him to campaign for a better future for Britain."
Sir Ed has been a member of the Liberal Democrats for 30 years, and acting leader since Ms Swinson left the role in December.
He was elected as an MP in 1997, but lost his seat of Kingston and Surbiton in 2015 after his tenure as a cabinet minister in the coalition government.
In the 2017 snap election, Sir Ed returned to Parliament for the same constituency and will now lead the party's 11 MPs and wider membership.
'Time to start listening'
In his victory speech, the new leader spoke of the task ahead, with the party only achieving single digit support in the the latest opinion polls.
"Nationally our party has lost touch with too many voters," he said. "Yes, we are powerful advocates locally. Our campaigners listen to local people, work hard for communities and deliver results.
"But at the national level. We have to face the facts of three disappointing general election results."
He added: "The truth is, voters don't believe the Liberal Democrats want to help ordinary people get on in life.
"It is time for us to start listening. And as leader, I have got that message. I am listening now."
New leader with old ties looking to move on
Analysis by Leila Nathoo, BBC political correspondent
This was Sir Ed Davey's second attempt to win the Liberal Democrat leadership - he lost out to Jo Swinson last year.
This time round, he comfortably persuaded party members that his years of experience in government and Parliament were in fact an advantage, and a better bet than his challenger's pitch for change.
Sir Ed acknowledged that his task now is to try to restore the party's fortunes.
It has just 11 MPs in the Commons after being punished over three general elections following the coalition with the Conservatives.
And the wave of defections during the heady days of the Brexit process turned out to be a flash in the pan.
The Liberal Democrats' Remain position was rejected by voters in 2019, and, now in a post-Brexit world - and with the Labour party too under new management - Sir Ed will be looking to move on.
He will hope that his focus on climate change can redefine the Lib Dems and help them regain national relevance one again.
Sir Ed also thanked Ms Moran for her "passionate campaign" and promised the education spokeswoman a "big role" in his team.
Former Lib Dem leader Tim Farron congratulated Sir Ed on his win, calling him a "fantastic campaigner who has the experience and vision to move our party forward".
And fellow MP Wera Hobhouse, who pulled out of the leadership race, said she looked forward to "a new positive future for our party".
The Lib Dems originally planned to delay the contest to succeed Ms Swinson until May 2021.
But the party brought it forward following criticism from party members.
The two-month contest began in June, but most hustings and meetings had to take place virtually due to coronavirus.
The party issued 117,924 ballots for the contest - the largest number in its history - and turnout was 57.6%.
Sir Ed won with 42,756 votes, while Ms Moran got 24,564 votes.
The margin was the largest of a Lib Dem leadership winner since the late Paddy Ashdown secured 71% of his party's vote in 1988.