Haaland, 21, who is widely tipped to leave Dortmund at the end of the season, netted twice in emphatic style having drawn a blank in his previous five games.
The thumping win over mid-table Wolfsburg leaves second-placed Dortmund six points behind Bayern, who are away to Arminia Bielefeld on Sunday.
Bayern, who exited the Champions League on Tuesday, are chasing a 10th straight Bundesliga title.
In spring sunshine, and in front of a capacity crowd at Signal Iduna Park, Dortmund turned on the style with five goals in a devastating 14-minute spell in the first half.
Tom Rothe, 17, marked a dream Bundesliga debut when the Germany Under-19 defender headed in Dortmund's opening goal from a corner after 24 minutes.
The floodgates opened with four more goals in quick succession.
Axel Witsel fired under the feet of visiting goalkeeper Koen Casteels, Manuel Akanji tapped in a free-kick and Emre Can scored with a long-range shot.
The Wolfsburg defence was shredded again when Marco Reus served up a tap-in for Haaland, who applauded his teammate after netting his first goal since late January.
It was the first time Dortmund held a 5-0 halftime league in Germany's top flight since April 2013.
Reus, who claimed assists for Akanji and Haaland's first goal, went close when he fired just over the crossbar.
Dortmund's captain then linked with Julian Brandt to release Haaland, who hammered in his second goal to make it 6-0 after just 54 minutes.
Wolfsburg grabbed a late consolation when Ridle Baku fired in the rebound after Dortmund goalkeeper Gregor Kobel's stunning save had denied Lukas Nmecha.