* Dutchman given three-year contract
* To take charge after World Cup
* Giggs to be his assistant after retiring from playing (Adds Giggs to retire from playing, Van Gaal's probable first game)
By Martyn Herman
LONDON, May 19 (Reuters) - Manchester United returned to a tried and trusted trophy winner after an ill-fated adventure with David Moyes when announcing that Dutchman Louis van Gaal had been handed the job of reviving the club's fortunes on Monday.
The 62-year-old, who has masterminded league titles at some of Europe's biggest clubs including Barcelona and Bayern Munich, and won the Champions League with Ajax Amsterdam, will begin the re-building job at Old Trafford once he has finished national duties at the World Cup.
Ryan Giggs, United's record appearance holder, will work alongside him after his four-game stint in charge following the sacking last month of Moyes, who was given the chance on the back of a long and worthy, but success-starved, 11-year stint in charge of Everton.
"In Louis van Gaal, we have secured the services of one of the outstanding managers in the game today, United executive vice-chairman Ed Woodward said in a statement that announced the Dutchman had signed a three-year contract and would start work after leading the Netherlands at the World Cup finals which start next month.
"Everyone is very excited about this new phase in the club's history. His track record of success in winning leagues and cups across Europe throughout his career makes him the perfect choice for us."
Van Gaal, who has already been working behind the scenes with United officials regarding potential transfers, is likely to take charge for the first time when United play LA Galaxy in a friendly in Pasadena, California, on July 23 - 10 days after the World Cup final.
"It was always a wish for me to work in the Premier League. To work as a manager for Manchester United, the biggest club in the world, makes me very proud," said Van Gaal, United's first manager from beyond the British Isles.
"This club has big ambitions; I too have big ambitions. Together I'm sure we will make history."
A year on from the bold decision to replace English football's most successful manager Alex Ferguson with fellow Scot Moyes - mainly on Ferguson's recommendation - the club's owners, stung by the financial impact of failure to qualify for the Champions League, have played it safe.
In Van Gaal they have recruited a manager who will command huge respect in the dressing room and in the transfer market and whose methods have stood the test of time.
He will need all his vast experience too as United attempt to repair the damage done by the 10-month Moyes era, which resulted in a seventh-placed finish in the Premier League.
The magnitude of the Old Trafford job appeared beyond Moyes but Van Gaal has sat comfortably - and certainly confidently - in some of the most pressurised hot-seats in world football despite occasional glitches and fall-outs.
His first task will be rebuilding the club's defence, which will be without Rio Ferdinand and Nemanja Vidic next season, and recruiting more pace and flair to a side that laboured last season, particularly at home.
Reviving striker Robin van Persie will also be key after the Dutchman suffered a disappointing campaign compared to his barnstorming impact the previous year when his goals fired United to a 20th English title.
United fans will be re-assured by Van Gaal's past feats.
He was responsible for nurturing great players such as Frank Rijkaard, Clarence Seedorf and Edgar Davids at Ajax who he memorably led to Champions League glory in 1995.
At Barcelona he won two La Liga titles in three seasons during his first spell from 1997-2000 while at Bayern Munich in 2010 he became the first Dutch coach to win the Bundesliga, unleashing rising German talents such as Thomas Mueller and Bastian Schweinsteiger and signing compatriot Arjen Robben.
Under Moyes, United's 2012-13 title-winning squad chronically under-performed, suffering an abysmal home record and humiliating thrashings by Man City and Liverpool.
The Scot's body language was defeatist at times and there was a suspicion that some of the club's senior players were less than impressed with his style of play.
Van Gaal, used to handling the egos of high-profile internationals, will have little time for dissenters.
While Moyes made the mistake of ditching Ferguson's backroom staff in his first days in charge, Van Gaal's acclimatisation at Old Trafford will be aided by the fact that Giggs, a hugely influential figure at the club, will be his right-hand man having announced on Monday that he his playing days are over having made 963 appearances in a glittering 23-year career.
"Louis is a world-class coach and I know I will learn a lot about coaching from being able to observe and contribute at such close quarters," Giggs said.
"Manchester United has been a huge part of my life and I'm delighted to be able to continue that relationship in such a key role."
Van Gaal will also bring Dutch goalkeeping coach Frans Hoek and scouting specialist Marcel Bout to the club as assistant coaches. (Reporting by Martyn Herman/Mitch Phillips, editing by Justin Palmer)