The 56-year-old German was the only player in the 144-strong field to master this links course overlooking the Bristol Channel, and the difficult conditions, to record a 13-stroke victory, the biggest in the 27-year history of the tournament.
He produced four sub-70 rounds to finish with a 72-hole total of 266 for a wire-to-wire success heralding a happy return to Wales, where he won his first European tour title - the Dunlop Masters - at St Pierre, Chepstow, in 1980.
His margin beats by six strokes the previous record-winning margin achieved by New Zealand left-hander Bob Charles at Turnberry a quarter of a century ago.
Langer, who posted scores of 65,66,68 and 67, also managed to defy yesterday's stiffening southerly wind blowing off the Bristol Channel. It appeared only a matter of how many he would win by once he had carded his third-round 68.
Before yesterday Langer's largest winning margin in a senior major was three strokes over Fred Couples at the 2010 US Senior Open.
The German was quickly out of the blocks with birdies at two of the first three holes and picked up two more on his way to the turn in 32 to stretch his advantage still further.
A momentary lapse cost him a bogey five on the 11th but he immediately made amends with a birdie two at the short 12th. Five pars followed before he put his second shot at the last on to the back of the green and took two to get down for a birdie four and a 67 for a 266 total.
"I just did not make too many mistakes. My driving was good and so was my long putting. I lacked concentration a couple of times but it really has been a wonderful week,"said Langer who now qualifies to play in next year's Open at St Andrews.
Montgomerie, aiming to become only the second golfer - after Gary Player - to win three senior majors in the same season following his two successes in the United States of America finished strongly with two birdies for a closing round of 69 - two under par, and for a 72-hole total of 279 (five under par).
The Scot started the day two under par and bogeys on two of the first three holes threatened to derail his hopes of a runners-up finish but he soon got his act together and reached the turn on level par. Seven pars followed before his back-to-back birdies to finish.
"I played solidly today. There was never any prospect of overtaking Bernhard so I did what was realistically the best I could - finish runner-up - and while it was not to be the treble I am pretty pleased with the overall performance," said Montgomerie.
The Scot collected a cheque for £131,550 but lost the leadership of the Charles Schwab Cup points table to Langer, and remains in second place to the German in the 2014 seniors money list.
Canadian Rick Gibson, England's Barry Lane and American Tom Pernice Jr finished in a tie for third place at two under par.
Tom Watson fell away in the last round with two double bogeys on the back nine in a disappointing 77, which gave him a 286 score - two over par - while Fred Couples also struggled in the wind, taking a closing 78 for 288.
Former European Tour professional Ross Drummond finished with a 75 for a nine-over-par total of 293 - he did not card a birdie yesterday - while Andrew Oldcorn, who made such a promising start on Thursday to be among the leaders, continued his slide with a closing 77 which comprised three bogeys and a double bogey for an 11-over-par aggregate of 295.
Kenny Hutton,the former Downfield professional who also started well, had two double bogeys and four bogeys in a homeward half of 44 for 78 yesterday and a 297 total.