'This is more than I expected,' said Donald, who was named to the European Ryder Cup team last Sunday. 'I knew I had the ability to win two tournaments but having the ability and doing it is something different.'
Miguel Angel Jimenez, who captured last week's BMW International Open, held a one-shot lead heading into the final round but struggled with a 72 to take second place at 14-under-par 270. Robert Coles fired a 64 to join Sergio Garcia, who shared the lead with Donald midway through the final round, and Eduardo Romero at 13-under-par 271.
Donald returned to the European Tour this year in an attempt to earn a spot on the European Ryder Cup team. It took little time for Donald to break into the win column at the Scandinavian Masters, and now the Englishman has shown once again why he was deserving of one of Langer's selections.
'I'm glad I made the decision to come over here and rejoin the European Tour,' said Donald, who was a winner on the PGA Tour in 2002. 'Everything's worked out just perfectly.'
The final group of Donald, Jimenez and Garcia began the day as the only legitimate contenders for the title at Crans-sur-Sierre. Donald broke away from his playing partners quickly with an eagle at the par-five first to move into the lead at 16 under.
'Sinking that putt got me off to a great start,' said Donald. 'A couple of hiccups, a couple of bogeys along the way, but every time I made a bogey I seemed to come back with a birdie and that was the difference.'
Donald hit his tee shot to 15 feet for a birdie at the par-3 third, but found trouble with a bogey at the fifth. He then birdied the par-4 seventh to find himself tied with Garcia, who picked up his third birdie of the day at the very same hole.
Garcia stumbled to a bogey at the eighth, but hit his third shot from a bunker to four feet at the par-5 ninth for a birdie to again join Donald atop the leaderboard.
Donald took advantage and kicked his second shot to the par-4 10th off of a hill and watched as it rolled within 12 feet of the cup. He drained the birdie putt and continued to lead despite a three-putt bogey at the 11th.
While Garcia was struggling at the 12th and Jimenez was unable to shake off his slow start, Donald played his approach inside 10 feet at 12 for a birdie to open a three-shot advantage.
Donald faltered to a bogey at the 13th, but recovered with a birdie at the par-5 15th. After a bogey at the 16th, Donald converted a 5-foot putt for a birdie at the 17th and hit his second shot to 8 feet at the closing hole.
The 26-year-old walked up the 18th fairway with cheers coming from the crowd, and applause from his Ryder Cup teammates, before sinking the putt to cap off the runaway win.
'All three of us being in the Ryder Cup, being in the last group, I think that's a strong message to send to the U.S. guys,' said Donald. 'It's great for European morale.'
Jimenez, who was gunning for his fifth victory of the season, tallied a lone birdie over his first nine holes. The veteran Spaniard managed a pair of bogeys on the inward half, failing to make a move down the stretch.
'I didn't play so good as I played the first three days,' Jimenez said. 'I tried hard but it happens. Luke Donald played very well, nice and solid. It's a good boost for the Ryder Cup Team.'
Graeme McDowell carded a 70 to finish alone in sixth place at 12-under-par 272. Ernie Els, who won this event last year, put his second shot in the water for a double-bogey at the 18th to complete a round of 71. Els was eight shots off the pace at 11-under-par 273.
K.J. Choi and Carlos Rodiles tied for eighth place at 10-under-par 274.