VfL Wolfsburg, who narrowly escaped relegation last season, joined them on six points after coming from a goal down to cruise past hosts Bayer Leverkusen 3-1 with their second upset in two matches.
Bayern were in complete control and should have scored long before Leon Goretzka fired in for the lead in the 37th minute.
Last season's Bundesliga top scorer Lewandowski added another in the 62nd with a fine low shot after Bayern hit the woodwork through David Alaba in a one-sided encounter.
Thomas Mueller of Bayern Munich celebrates with teammate Robert Lewandowski after scoring his team's third goal during the Bundesliga match between VfB Stuttgart and FC Bayern Muenchen at Mercedes-Benz Arena on September 1, 2018 in Stuttgart, Germany.Getty Images
The Poland forward then turned provider, sending Thomas Mueller through with a well-timed backheel flick for their third goal in the 76th to put the game beyond Stuttgart.
Wolfsburg, who stunned last season's runners-up Schalke 04 2-1 on the first matchday last week, scored three times after Leon Bailey's lead for Leverkusen.
Keeper Ramazan Ozcan slapped the ball into his own net for an own goal in the 36th-minute, Wout Weghorst headed in after 55 minutes and Renato Steffen fired in a third on the hour for Wolfsburg, who had survived a relegation playoff last season to stay in the Bundesliga after finishing 16th.
Players of VfL Wolfsburg celebrate following their sides victory in the Bundesliga match between Bayer 04 Leverkusen and VfL Wolfsburg at BayArena on September 1, 2018 in Leverkusen, Germany.Getty Images
Champions League club Hoffenheim bounced back from their opening loss to Bayern and beat Freiburg 3-1 courtesy of forward Adam Szalai's second-half double and Andrej Kramaric's stoppage-time goal.
Schalke host Hertha Berlin on Sunday.
This article was written by cool news network.