Leipzig's shock 1-0 defeat at bottom side Ingolstadt, who finished with ten men, ended their three-week stint as leaders.
Carlo Ancelotti's Bayern cut the three-point gap and regained top spot on goal difference with both teams on 33 points.
"We're top of the table again -- that'll be good for our Christmas party!" quipped Thomas Mueller, who scored his first league goal in 999 minutes, before Bayern's festive celebrations on Saturday night.
Second-placed RB had their 13-match unbeaten run ended -- a record for a club at the start of their first Bundesliga season -- as coach Ralph Hasenhuettl endured a horror return to Ingolstadt, who he left last season.
"Defeats always hurt, it doesn't matter against who," said Hasenhuettl, whose side battered the Ingolstadt goal with 13 shots to the hosts' four.
"The opponents forced their own game on us, we had little influence and didn't show enough courage. We were better after the break, but we couldn't make our 300 percent (more shots) count. The ball didn't want to go in.
"This is a set-back, but we can handle it."
Ingolstadt had Australia striker Mathew Leckie sent off for two yellow cards in quick succession late on, but his team held on and the win took them off bottom leaving Darmstadt, who lost 1-0 at Freiburg, last.
Bayern and Leipzig are now six points ahead of nearest rivals Hertha Berlin, who suffered a shock 1-0 home defeat to Werder Bremen after Germany striker Max Kruse scored the first-half winner.
Bayern host Leipzig on December 21 at Munich's Allianz Arena, where the hosts romped to a heavy win over Wolfsburg.
The 2015 German Cup winners have fallen from grace and defeat leaves Wolfsburg 15th, only clear of the relegation zone on goal difference.
Head coach Valerien Ismael, who took over after Dieter Hecking was sacked in October, left Germany's attacking midfielder Julian Draxler out of the squad.
The 23-year-old cost 35 million euros ($37.3m) from Schalke in August 2015 and Wolfsburg say they are open to sell him in January's winter break.
Bayern started with Jerome Boateng on the bench with a shoulder injury and his centre-back partner Mats Hummels was missing with gastroenteritis.
Arjen Robben opened the scoring by curling his superb shot around Wolfsburg's goalkeeper Diego Benaglio on 18 minutes.
Reus rescues Dortmund
Lewandowski netted five goals in a record nine minutes in the same fixture in September 2015.
On Saturday, the Poland hot-shot needed just 21 minutes to get on the scoresheet.
To compound Wolfsburg's problems, defender Marcel Schaefer went off with a knee injury after 23 minutes as it finished 2-0 at the break.
Lewandowski added his second on 58 minutes, Mueller grabbed his first league goal of the season by firing home Robben's pass on 76 minutes then Brazil winger Douglas Costa added Bayern's fifth just before the whistle.
Fresh from their 2-2 Champions League draw at Real Madrid, Borussia Dortmund needed a 90th-minute Marco Reus goal to rescue their 1-1 draw at ten-man Cologne.
Cologne took the lead when Germany defender Jonas Hector fired in a long-range free-kick and Artjoms Rudnevs slipped his marker, heading past Dortmund goalkeeper Roman Weidenfeller on 28 minutes.
But Reus rescued a point when he cooly slotted Adrian Ramos' cross for a point which kept Dortmund sixth as Cologne had Salih Ozcan sent off late on for a second yellow.
Hamburg stay in the bottom three despite their 1-0 home win over Augsburg as both sides finished with ten men.
The hosts took the lead when Nicolai Mueller hit the post and Serbia international Filip Kostic converted the rebound on 68 minutes.
Hamburg had Lewis Holtby sent off just before the break for lashing out after Augsburg's midfielder Dominik Kohr's rough tackle.
But Kohr was also shown a red when he earned his second yellow soon after.
On Friday, Hoffenheim were held to a goalless draw at Eintracht Frankfurt but are now the only unbeaten team in Germany's top flight.