The referee blows the final whistle. A straightforward win for Bayern in this top-of-the-table contest. The hosts scored three times in the first half and take their place at the Bundesliga summit on goal difference from Borussia Dortmund. Union Berlin are in third place after their loss.
Musiala tries to tee up a fourth goal but his pass is too close to Rönnow, who saves easily.
Speed check: The fastest player in the game after 90 minutes
A lovely, flowing move from Bayern sees Sane racing down the left. He rolls in for Mane who hits it first time for the charging Davies. The full-back's shot finds Rönnow's outstretched boot.
Pavard in the book
Pavard sees yellow for a block on Leweling.
Big shot count
9 off target
9 on target
3 off target
1 on target
Sane's back pass is lazy and allows Behrens in to feed Seguin. Sommer saves the subsequent shot. That was a let off for Bayern.
Changes all round
Nagelsmann sends Cancelo and Sane into the game while Haberer is on for the visitors.
Bayern on the hunt
Gnabry lines up a shot and drills inches wide of the post. No lack of hunger from the hosts, who are intent on getting a fourth.
How on earth?
Mane is suddenly in on goals. Will he score on his comeback? The Senegalese unselfishly squares for Müller who shoots from point-blank range. Rönnow heads the ball over the bar. Interesting reaction save.
Bayern win a couple of corners after some good work by Gnabry. Kimmich fails to make the set-pieces count, however.
Niko Gießelmann comes on for Union with Roussillon limping off with an injury, which looks muscular.
Sadio Mane is back!
Welcome back Sadio Mane! The Bayern attacker makes his long-awaited return from injury after 110 days out. Serge Gnabry is also on for the record Bundesliga champions.
Fischer sends Seguin, Behrens and Leweling into the game.
Coman frees Müller who darts a shot at goal from a tight angle. Rönnow saves with his coupon.
Distance run (km)
Joshua Kimmich Morten Thorsby
Becker's shot fizzes towards the target, hits the pole behind the goal and makes the net wobble. The Union fans mistakenly shout "Tor". Becker raises his hand pleading for a corner, which his team are awarded. Nothing doing from the resulting Trimmel set piece.
A flighted ball into the Bayern box has Sommer scrambling to take possession ahead of Trimmel. The Bayern keeper loses it before snaffling the ball back into his body.
The hosts are unsurprisingly the likelier of the teams to score the game's next goal.
Bayern goal favourites
It's snowing again, heavily.
Musiala off target
Davies again in possession plays the ball back for Musiala, whose shot is high, too high.
More from Bayern
Davies is in on goal and facing Rönnow. Canada's finest swipes low and looks on as the ball thwacks the Union goalkeeper's elbow.
Union were also 3-0 down at the break here at the Allianz Arena last season. What will Urs Fischer have told his players at half time?
Off we go again
Bayern kick off the second half. It's stopped snowing.
This one is all but over at the break with Bayern turning their domination into goals, three of them, in the opening first half. The hosts are heading back to the top of the standings on goal difference as things stand.
Happy Birthday Jamal
Goodnight Berlin. Musiala has a goal on his birthday. Coman - again involved - plays Müller in on the right. Bayern's captain gets to the byline, just about keeps the ball in and cuts back for Musiala, who rattles home from close range.
Kingsley Coman has scored in three consecutive Bundesliga games for the first time. What a top player he is.
Bayern at the double
Bayern double their lead. Flekken's goal kick is headed straight back in the opposite direction by De Ligt. Müller snaps a pass into the path of the onrushing Coman, who takes it around Flekken and slides into the empty net. Simples.
Choupo-Moting makes it nine
Jordan knocks it to Becker on the right and from inside the area, the Union forward passes invitingly to Laidouni. The Union No. 20 blooters one high and wide. That was a serious chance for the visitors.
Bayern look to break and Musiala is onto the ball in a flash. For a second, the attacker looks to be away through the middle. Thorsby pulls his shirt, then his shorts, then wraps his arms around Musiala, who gets fed up trying to escape. Yellow card for Thorsby, unsurprisingly.
Choupo-Moting and in
Bayern lead. Becker fails to put his foot on the ball and it rolls to Coman who lifts a pass right into the mixer. Up goes Choupo-Moting, rising above the defenders, to send a header back across Flekken and in at the far post.
Eric Maxim Choupo-Moting
High ball dropping into the area and Müller is setting himself. An acrobatic swoosh from the Bayern captain propels the ball goalwards. Rönnow parries out.
Speed check: The fastest player in the game after 30 minutes
Morten Thorsby has brought his A game to the Allianz Arena, the Union man winning all five of his duels so far.
Davies pokes Musiala in and this looks like 1-0. The 20-year-old smacks one from close range, but Knoche slides along the snowy surface and makes a brilliant block.
Shot count increasing
2 off target
1 on target
0 off target
1 on target
Becker is down the right and smacks one into the centre. Jordan whirls his hands into one of those overhead kick wind ups before launching himself into the air. If this comes off it'll be a goal for the ages. It does not come off.
FCB on the move
Back we go with Bayern and it's Musiala - after some heavy pressure from the hosts - who darts in from the left before seeing his pass stopped by Rönnow. Soon afterwards, Coman chips a pass in for Choupo-Moting, who will never reach that.
And the counter chance comes now. Roussillon is into the home area but rather scuffs his shot - or was that a pass - and the ball ends up with Sommer. At the other end, Choupo-Moting pokes an effort into Rönnow's hands.
Berliners take shape
Union are keeping everyone bar striker Jordan behind the ball when the record champions are in possession. It's a compact set-up by Urs Fischer, whose side will look to counter when the opportunity arises.
Bayern bossing it
Union's midfielder stretched to reach a ball with Kimmich and got a whack on the shin for his troubles. The visiting No. 8 stays down for a time but soon gets back to his feet and hobbles on.
Birthday boy Musiala can't quite catch his shot on the full and the ball dribbles wide.
Bayern in command
Choupo-Moting dinks a pass into the Union area that causes all sorts of confusion. After a bit of pinball, the visitors hoof clear.
No go Müller
Davies plays a superb pass in for Choupo-Moting, who rounds Rönnow and passes back for Müller. Bayern's captain can't make it count and that will go down as a big chance missed.
The ball is holding up a tad on the snowy surface. Not ideal for Bayern's passing game. Union won't mind if this puts the hosts off all that much.
Coman is already causing problems down the right and the France international wins a corner. Kimmich takes, Union clear. De Ligt puts the loose ball onto the roof of the net.
Off we go!
Union kick off and it's game on.
Almost time ...
Captains Müller and Trimmel join the ref for the coin toss and we're almost ready for the off amid a snow storm in Bavaria.
A blizzard has descended on the Allianz Arena as the players make their way out onto the pitch.
Teams in tunnel
Both sets of players are lining up inside the tunnel as the atmosphere outside booms and crackles ...
Watch: Fan-tastic Union
First time for everything
Union have never beaten Bayern in seven attempts, but have held the record champions to three draws, including earlier this season.
Watch: The Union Berlin fairy-tale
Watch: Union in the house
As expected, Trimmel is rotated in at right-back for Juranovic. Thorsby gets the nod over Haberer in midfield, while US striker Jordan makes only his second start of the year. Behrens makes way.
Union starting line-up
Rönnow - Doekhi, Knoche, Diogo Leite - Trimmel (c), Laidouni, Khedira, Thorsby, Roussillon - Becker, Jordan
Grill, Jaeckel, Juranovic, Gießelmann, Seguin, Haberer, Michel, Behrens, Leweling
With Upamecano suspended, Nagelsmann throws a curve-ball by naming Stanisic in a back three alongside Pavard and the recalled de Ligt. Davies, Musiala and Coman are also restored to the side, with Cancelo, Blind, Gnabry and Gravenberch making way. Sadio Mane is back on the bench following three months out.
Bayern starting line-up
Sommer - Pavard, de Ligt, Stanisic - Coman, Musiala, Kimmich, Goretzka, Davies - Müller (c), Choupo-Moting
Ulreich, Blind, Cancelo, Sarr, Gnabry, Gravenberch, Sane, Mane, Tel
Watch: The calm before the storm
Dortmund moved top with victory over Hoffenheim yesterday. They're on 46 points, with Bayern and Union three further back.
Watch: The title race, powered by 442oons
Watch: Musiala magic
Nagelsmann: "We can't make mistakes"
© Boris Streubel/Bundesliga/Bundesliga Collection via Getty Images
Watch: All you need to know ahead of Bayern vs. Union
Will "the madness continue" today?
© Maja Hitij/Getty Images
Watch: Spoils shared earlier in the season
Top-spot up for grabs
Sunday's headline act on Matchday 22 sees Bayern host Union in an encounter that has top-spot up for grabs. Will the defending champions be able open up a slender lead, will unlikely title-hopefuls Union put a major flag in the ground or will - as we've seen so far this season - there be nothing to separate the top-two?
Watch: Get ready for Bayern vs. Union!
Here you can find all the information about FC Bayern München against 1. FC Union Berlin on matchday 22.