That suggests that he will get off to a flying start at Old Trafford - but his history at both Bayern and Barca strongly indicates that any on-pitch success will come at the cost of terrific battles off it.
Throughout his career he has consistently alienated superstars - among them Brazil legend Rivaldo while at Barcelona, and France superstar Franck Ribery at Bayern - and upset the applecart.
In fact, far from being grateful for all he did, Bayern Munich's president Uli Hoeness once went on the record to say: "His problem is that Louis is not God, but the father of God. Before the world existed, Louis was already there."
It's hard to actually envision the level of arrogance that must have provoked such a statement. What's far less hard to imagine is that it will lead to clashes at the already-crisis-stricken Manchester United.
You can see where we're going with this already. If there's one player you would NOT back to keep his mouth shut and toe the line under a strict new regime, it's Wayne Rooney. And there is a very real chance that Van Gaal's arrival will also herald Rooney's exit.
Twice in the past four years Rooney has threatened to leave Manchester United; twice he has relented, and signed a new (and much improved) contract to keep him at the club. But the bald fact is that Rooney has only surpassed 20 goals once in the last four seasons, and many raised eyebrows at the generosity of the £300,000-a-week contract he agreed recently.
Several papers reported the Scouse striker's "fears" over Van Gaal's appointment in the last few weeks, suggesting that there could well have been a few off-the-record briefings by either the player himself or his manager. Van Gaal is expected to restore Robin van Persie as the Red Devils' number one striker - leaving Rooney either on the bench or being played out of position. In other words, the exact same unsatisfactory situation that almost prompted the England star's exit last summer. Rubbing a little extra salt into that wound, Van Persie is also expected to take over as club captain instead of Rooney.
Would Van Gaal really have the guts to sell off a United icon, however? We'll answer that question with an anecdote: during his second spell at Barcelona, Van Gaal was once challenged in the dressing room by players over whether or not he had the balls to drop the club's big stars. He replied by dropping his trousers in front of the assembled squad before yelling that yes, he did have the balls, and here was proof.
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- Manchester United
- Bayern Munich
- Wayne Rooney
- Louis van Gaal