Jim Murphy MP is the new leader of the Scottish Labour Party, comfortably beating Holyrood health spokesman Neil Finlay and former Scottish Executive minister Sarah Boyack.
The East Renfrewshire MP and former Secretary Of State for Scotland had been favourite to win the race triggered by by the resignation of previous leader Johann Lamont.
After the announcement, Mr Murphy, who received 55.77% of the vote, said: "Today is the fulfilment of a dream for me."
Speaking to Labour party members at the Glasgow Emirates Arena, he joked that he had always dreamed of being appointed captain of a team in the east end of Glasgow.
He said becoming leader was a "remarkable honour".
"Scotland is changing and so too must Scottish Labour. I'm ambitious for our party because I'm ambitious for our country."
Mr Murphy told Sky News' Anna Jones: "This is fresh start for the Scottish Labour Party. We are going to do things differently. It's a new beginning. We are going to identify new policies and a new approach.
"I want us to use our passion and ingenuity to change our country. I know we can do it if we work together.
He said he would be the one making the decisions for Scottish Labour, not Westminster.
"I am big enough and ugly enough not to be pushed around by anyone. I'll make the decisions, we'll call the shots here in Scotland.
"The Scottish Labour Party is back in business."
Polls indicate that Labour could be routed in Scotland at May's General Election, as support for the SNP rises, but Mr Murphy said he was determined to change that.
He said most Scots want David Cameron out of Downing Street and warned that only Labour was big enough to do that.
Congratulating Mr Murphy and new deputy leader Kezia Dugdale, Labour leader Ed Miliband said: "I look forward to working with both Jim and Kezia to secure a Labour government in Westminster next year and Holyrood the year after."
Offering her congratulations, Scottish National Party leader and First Minister Nicola Sturgeon said: "I know that the challenges of leadership are never easy, so I offer my best wishes for the job they have ahead.
"While we will undoubtedly cross swords often in the months ahead, my door is always open to those who wish to find common ground and work together in the best interests of people in Scotland - something I hope we will have the opportunity to do."
Ms Lamont stepped down in October, criticising the party's UK leadership for treating Scottish Labour like "a branch office of London".
The Scottish Trade Unionist and Socialist Coalition, which had backed Mr Finlay, said: "The election of Jim Murphy to the position of leader of the Scottish Labour Party is a devastating blow to those members, and particularly the affiliated trade unionists ... hoping to turn Labour to the left."