Goals from Steven McDougall and David Graham gave Dunfermline a win over Morton to secure the Division One title and a place in Scotland's top flight.
Joe Cardle tested Colin Stewart with a 20-yard strike in the third minute before McDougall opened the scoring four minutes later from close range.
Andy Kirk and McDougall both went close to extending the Pars' lead.
But Graham added a second five minutes after the interval when he found the bottom corner from 20 yards.
Morton searched for a way back into the game and almost pulled a goal back, but Pars goalkeeper Chris Smith managed to parry Allan Jenkins' lob to safety.
Dunfermline's victory meant that Raith Rovers could not catch their Fife rivals no matter their result against Queen of the South.
And, with Rovers losing 1-0 at home, the Pars now have a seven-point lead.
The Pars will now be able to celebrate the Division One title next weekend at home to third-top Falkirk, who lost at home to relegation-threatened Ross County, as they end a four-year absence from Scotland's top flight.
Manager Jim McIntyre told BBC Scotland: "It is a great feeling to get over the line and that's what we've been striving for all season.
"We didn't want it to go to next week. Obviously, with the way results went elsewhere, it wouldn't have mattered anyway, but we weren't to know that.
"I thought the boys' approach was spot on. We came out the traps and should have been further ahead by half time.
"We have done it with some style."
McIntyre was looking forward to a weekend of celebration but pointed out that he would be meeting with director of football Jim Leishman to plan for building a team that can hold their own in the SPL.
"You've got to strengthen," he said. "I'd be foolish to think otherwise, but I think we've got a nucleus that is capable."
Leishman, who led the Pars to the top flight as a manager, paid tribute to McIntyre, the club's fans and their rivals for the title.
"Jim McIntyre deserves a lot of credit," he said. "He's a young manager with his first club and this is for all the hard work he's put in.
"Jim has taken over at a hard time. A lot of players were leaving at the time he took over and we have had to work hard to get the income matching the expenditure.
"He has managed his budgets very well and now we are starting to get on an even keel - and today was fantastic.
"I've seen so many promotions with Dunfermline as a manager and I can really understand what it feels like for Jim McIntyre today.
"John McGlynn deserves a huge amount of credit for what he's done for Raith Rovers and Steven Pressley came with a late run with Falkirk, but all credit to Jim McIntyre for withstanding the pressure and producing.
"It is a great occasion for Dunfermline next week getting the league championship in front of our fans.
"But the works starts on Monday, when I have a meeting with Jim McIntyre, and he now knows where we are and will be looking to sign new players."
Morton: Stewart, MacGregor, Evans, McCaffrey, McKinlay (Monti 46), Lyle (Holmes 73), Jenkins, Bachirou, Tidser, O'Brien, Weatherson (Kean 63). Subs Not Used: Cuthbert, Young.
Dunfermline: Chris Smith, Woods (Phinn 75), Keddie, Rutkiewicz, McCann, Graham, Mason, Dowie, Cardle (Buchanan 82), McDougall (Clarke 63), Kirk. Subs Not Used: Paterson, Higgins.
Goals: McDougall 8, Graham 51.
Ref: Brian Winter