The 62-year-old will start his job when his duties with the Dutch national side come to an end at this summer's World Cup in Brazil.
While his appointment has largely been met by positive noises, it is widely accepted that Van Gaal has a huge task on his hands if he is to return the Red Devils to the higher echelons of English football.
Here, Sports Mole has picked out five immediate tasks that the former Barcelona and Bayern Munich head coach will have to contend with at Old Trafford.
1. Incomings and outgoings
Between them, David Moyes and chief executive Ed Woodward turned last summer's transfer window into a car crash. On occasions Moyes went public with his targets (namely Cesc Fabregas), while Woodward was said to have submitted numerous offers to clubs for their players that were painfully under valuation. The result? United ended up signing just Marouane Fellaini on deadline day for a hefty £27.5m from Everton, although under the terms of his contract at Goodison Park, the Belgian could have been recruited for around £4m less earlier in the summer.
Twelve months on, Van Gaal cannot afford to mimic his predecessor. With his standing in the game, it is expected that he will find it easier to lure players to the club than Moyes. What's more, he's even gone as far as stating that he has made Woodward and the board aware of the players that he requires to get United back up to their fighting weight. Among the reported targets are Luke Shaw, Mats Hummels, Toni Kroos, Fabregas, Thomas Muller and Arjen Robben. While securing all of them is nigh on impossible, any would make a significant improvement to the starting lineup.
The departures door also needs to be revolving. Experienced centre-backs Nemanja Vidic and Rio Ferdinand have already exited, while Ryan Giggs has hung up his boots to concentrate fully on assisting Van Gaal. Yet, there still remains plenty of deadwood in the squad. The number of players that leave will obviously depend on how many arrive, but the likes of Tom Cleverley, Ashley Young, Nani, Darren Fletcher, Shinji Kagawa and Javier Hernandez to name a few could all be looking for pastures new.
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Had Moyes have been given another campaign to prove that he was up to the job, it looked increasingly likely as the season progressed that Wayne Rooney, whom he had convinced to remain at the club, would replace the departing Vidic as captain. Then, when Rooney penned his reported £300,000-a-week contract extension, the destination of the armband looked inevitable.
The appointment of Van Gaal, though, has thrown a spanner into the works. Rooney's club teammate, Robin van Persie, is the new manager's choice of skipper with the Dutch national side and as a result is the odds-on favourite to be handed the responsibility at Old Trafford. Speaking recently, Van Gaal said of his compatriot: "I think you always make a player captain when you have the same morals and philosophy as they do. Not only about football and tactics and what is happening on the pitch but about life as well. We click and I think that's very important. I believe that Van Persie and Van Gaal share the same philosophy."
Rooney welcomed the arrival of Van Gaal on Twitter yesterday, but having had his nose put of joint after what he perceived as being played as second fiddle to Van Persie during Sir Alex Ferguson's final season at the helm, it will be interesting to see which of the two strikers Van Gaal opts to lead his team.
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3. Relationship with Giggs
In an interview late last year, Van Gaal stressed that he liked to have someone on his coaching team that has a strong working knowledge of whichever club that he is in charge of. Therefore, Giggs, who has 23 years of playing experience with the United under his belt, seemed the logical choice. Sceptics, though, have suggested that the delay surrounding Van Gaal's appointment centred around who would be his assistant.
Dutch newspaper De Telegraf, who followed the story extremely closely, had claimed that the incoming boss was very keen to be joined by Patrick Kluivert, but the powers that be at United were eager for Giggs to remain with the club. For his part, it was believed that the veteran midfielder wanted to be the assistant, rather than just being given a coaching role, having had a taste of management during his brief interim spell towards the end of the season.
Giggs has prevailed, but it's now time to see if the two can work together. The pair will need to form a working relationship, perhaps even immediately because with Van Gaal at the World Cup, transfer targets will need to be tempted to the club. Despite his loyalty to those in the dressing room, Giggs must also be brutal in telling Van Gaal which players are not up to the standard required.
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4. Reinvigorating youth talent
When Ferguson retired in 2013, he insisted that Moyes would inherit a good squad full of young talent. He didn't name names, but it was assumed that he was talking about David de Gea, Rafael da Silva, Phil Jones, Chris Smalling, Cleverley and Danny Welbeck. Last term saw teenager Adnan Januzaj materialise as one of Europe's finest talents, but aside from De Gea, who excelled between the posts, the rest struggled to live up to expectations.
If retained by Van Gaal, those that failed to fulfil their potential will not have a better chance to succeed at the club. This is a man that won the Champions League with Ajax in 1995 with a team packed full of talented youngsters, while he also handed debuts to Victor Valdes, Xavi and Andres Iniesta at Barcelona, as well as Thomas Muller and David Alaba at Bayern Munich.
Van Gaal's reputation may also capture the attention of striker James Wilson, who on debut against Hull City earlier this month scored twice. That philosophy may have an impact on Van Gaal's transfer dealings as well, with Southampton's 18-year-old full-back Shaw a reported top target.
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Former United striker Dwight Yorke summed up the club's demands yesterday when he told Sky Sports News: "Man United is based on results and last season was appalling. They are looking to get back some credibility and competing in the Premier League, where Man United belong."
In short, Van Gaal must hit the ground running in terms of results. On reflection, Moyes's tenure looked doomed from the beginning. After a convincing 4-1 win over Swansea City on the opening day, United had collected just seven points from their opening six Premier League encounters. That run included defeats to rivals Liverpool and Manchester City, as well as a dour draw with Chelsea. It's the sort of start that Van Gaal cannot afford to oversee.
Unlike Moyes, the Amsterdam-born coach has a serial winning mentality to call upon. He has won league titles with each of the four clubs that he has managed, as well as domestic cups with three of those. When considering the managers that were available to United, Van Gaal, with his track record, appears to be safest bet. Now, though, he must put that into practice.