The German Cup was won by Rangnick with Schalke in 2011.
The interim Manchester United manager will be named by the end of the season.
He will take on a consulting role with the club for two more years after his initial six-month spell in charge.
What attracted United to Rangnick? What kind of manager is he? Is he likely to be a success and what will his role be after this season?
What will his appointment mean for him?
The questions were answered by the St. Louis SC sporting director, Christian Fuchs, Raphael Honigstein and Guillem Balague.
The best man on the market.
The appointment of Rangnick comes at the end of a thorough recruitment process conducted by United, who were impressed during an initial conversation with the German earlier this week.
The 63-year-old has built an impressive coaching reputation during his time in Germany, chiefly through spells at Hoffenheim, Hoffenheim, and RB Leipzig.
He would be joining a club that is eighth in the league, having lost their way under Solskjaer, who ended up with a fourth defeat in five league games.
Honigstein said that he had a similar offer of an interim job from Chelsea a long time ago. There are three things in this case.
Manchester United has a special ring to it. A romance can be found for an anglophilic like Rangnick, who studied and lived in England and loves the premier league.
It is six months. A lot of football is still to be played.
He was told by United that they might only want him as a short-term manager, but they wanted to tap into his football knowledge. At a time when the structure at United is changing, with a new chief executive coming in, and an openness to bringing in more football expertise from outside, this is a good time to do this.
We all look at what Thomas Tuchel has done in a short period of time. He has no experience of English football, comes in January and gives a team that was rudderless some structure, and he goes on to win the title.
I think United will have wondered if they could get a Tuchel-type guy to give them an immediate lift. The team is doing better than they are currently doing.
Pfannenstiel says that Ralf is one of the best coaches or managers Germany has produced in the past 15-20 years.
He wants to work for a big club in England if he gets the chance, and everything he has done so far has been successful.
I think the interim head coach is the one who can get everything in order and get United back on track. I think he was the best man on the market.
Laurens is gobsmacked but still not sure. He's one of the greatest minds in football over the past 20 years.
You don't do that in six months if he's a builder.
I wouldn't put him in that role for a quick fix. He will give his opinions, but won't be able to interfere like he did at Leipzig. I was surprised. I can see why he took that job, you can't say no to United.
He has never managed or played football in England.
'Pressing, high-intensity and always exciting to watch'
His influence on the game is vast, not only as a coach and director of football, but as a thinker on the game, even though his trophy haul as a manager is modest.
Hoffenheim and RB Leipzig are his biggest achievements.
He has influenced many people, including Tuchel, Hoffenheim, Hasenhuttl and Klopp.
Pfannenstiel: His football is very direct, lots of pressing, lots of counter-pressing, lots of high-intensity football, something which is always exciting to watch.
If you look at how Hoffenheim played, you can see that they pressed and stressed the opponent, forcing them to make mistakes.
Everything he does is with a clear goal. He isn't a guy who jokes all day. He wants things to get done and will approach them that way. I think he will always be successful because he is as intense as his football will be. He expects a lot from the players, but also a lot from himself.
I think it's a good fit for the style the fans love to see at Old Trafford and for the players Manchester United have. I believe that Ralf could be the next German who puts his stamp on a club's future.
He has a clear idea of how he wants to play, and that will never change.
He wants to have a conversation with you. I was in Vienna with the Austria national team and we had a couple of beers and talked about Hoffenheim for a long time.
He said that he wasn't the player for him at the moment.
He was very straightforward and up front. He said he wanted to sign you now.
He thought I was not ready, but that's all credit to him for being very straightforward and realistic. Two years later, he said 'now, you are ready', after he said'keep playing, keep learning'.
The positioning, when to push forward, and all of the other little things can have a huge impact on your game. He made me feel comfortable and appreciated when I arrived at the big club. This kind of man-management is important in the game.
He knows what he wants and he will demand that the players stick together.
It is thought that Michael Carrick will remain in charge at United after this weekend's game with the Blues.
It is going to be difficult if he doesn't want him.
United will be the first club that Rangnick will manage that is truly elite.
He joins them after a summer of investment during which they added a number of high-profile players to a squad already loaded with internationals carrying big reputations.
Honigstein said that he has always been nice with people, but some people can't handle someone who wants to change quickly. They find it exhausting to find someone who pushes you. Some players respond well and go to the next level.
The problem for Rangnick has been the people upstairs because once you are in a certain position it becomes about keeping your job rather than doing your job. These types have been threatened by people who say they need to change something.
It looks like it's an interim job. If you're creating a new structure, Ralf is someone who knows what he has to do.
I think there's a lot of people at United that don't want to change. You have to be nice to people. Is he nice now?
There is a lack of clarity in decisions at United.
He won't have as much authority as a guy who comes in on a three-year deal, but he can do whatever he wants. He can be more ruthless.
It is going to be difficult if he doesn't want him. It's not so easy to figure out how doesRonaldo fit in with the kind of football that Rangnick likes. Maybe he can. Maybe the idea can change. One of the most fascinating parts of the story will be it.
Even if they are not on the same wavelength, Ralf has learned to deal with them. The excitement of six months at Manchester United will take its own dimensions.
The future is really brilliant.
Since 2012 he has worked in a number of high-profile sporting director roles, most notably with the Red Bull stable of clubs and the club that rose from the fourth tier of German football to challenging for the title.
He is the head of sports and development at Lokomotiv Moscow.
Honigstein is not sure if that role will have real power. I don't think United is ready for that.
He is at a point in his career where he has set up his own consulting company and is working with clubs, federations and sporting directors.
I think he wants to give what he has learned to someone else. They pay him for his advice and if they don't like it, he leaves. I think he is different than the guy who comes in and has to have full control.
Pfannenstiel: He's the football professor in Germany. The way he puts structures in place at every club is amazing.
A lot of science is involved in the way Red Bull Salzburg was built and the way RB Leipzig was built. The future is brilliant because of his organisation, structure and planning.
He wanted to be more on an advisory side after finishing his deal in Leipzig, so he went to Moscow to do that.
I think the plan to be an adviser in the next two years after this season is a good one, because I know how the football world works and I think everybody will be happy if he comes in and does an unbelievable job.
Everything is possible and I think it's all about results and being successful.
