Two days after Barcelona beat Manchester United at the same stadium to win the Champions League, Scott Sinclair's hat-trick, including two penalties, and a Stephen Dobbie goal earned Swansea victory in a game worth an estimated 90 million pounds.
Swansea, who finished third in the Championship behind promoted Queens Park Rangers and Norwich City, swept into a 3-0 halftime lead with some Barca-like football but Reading roared back with a Joe Allen own goal and a Matt Mills header.
However, Sinclair struck his second penalty with 10 minutes remaining to ease the nerves of 40,000 Swansea fans inside the stadium and return the club to the top echelon for the first time since relegation in 1983 sent them into turmoil.
"It's a great credit to the club, the fans were incredible and it was important to repay their faith in us and get promotion," Swansea manager Brendan Rodgers, who had a spell as Reading coach, told Sky Sports.
"It was a fantastic game, we didn't play as well as we have done for the rest of the season but in the moments we showed quality we were very good. I think ourselves, Norwich and QPR will be a credit to the Championship."
Promotion completes a remarkable turnaround for the south Wales club who nine years ago were on the brink of going bust and a year later needed to win on the final day of the season to avoid dropping out of the Football League.
Since then they have been on the up, re-locating from their atmospheric but crumbling old Vetch Field Stadium alongside Swansea Bay to the gleaming Liberty Stadium and moving through the divisions with an attractive brand of football.
They are the first Welsh club to play in the Premier League since it was formed 1992 and the players marked the biggest day in the club's history with T-shirts bearing the name of former player Besian Idrizaj who died last year aged 22.
Swansea, who were last a top flight side under the management of former Liverpool player John Toshack, began nervously but settled into their fluid passing game once Sinclair calmly slotted a penalty after Nathan Dyer was tripped by Zurab Khizanishvili after 21 minutes.
A minute later Sinclair doubled Swansea's lead with a tap-in from Dobbie's low cross and Dobbie, who was part of Blackpool's promotion-winning side last season, seemed to have killed Reading off after 40 minutes with a first-time finish.
Reading, who spent two years in the Premier League from 2006-08, got a lifeline when Allen deflected a header into his own net and a remarkable comeback looked on when Mills clawed another one back with more than half an hour remaining.
Swansea had huge let-off when Jem Karacan struck a shot against the post and when Sinclair restored their two-goal margin the Welsh celebrations could begin.
