European spots are also up for grabs alongside one of the tightest relegation battles in recent memory as the campaign comes to an end.
At the top of the table, Dortmund know a win over mid-table Mainz will secure the title, while Bayern can claim their 11th straight championship with a win at Cologne, if of course the leaders slip up.
Dortmund manager Edin Terzic called on his side not to lose focus, with one game to play.
"We're not done yet, but we're ready to take the final step," Terzic said, "As a team, as a club, as a city."
Terzic was called "the best Dortmund coach since Jurgen Klopp" on Thursday by Germany's Sueddeutsche Zeitung newspaper, putting the 40-year-old ahead of Bayern boss Thomas Tuchel, perhaps a sign how far the former Chelsea mentor's stock has fallen since taking the job.
Bayern have closed ranks ahead of a week which could see them go trophyless for the first time since 2011-12, but veteran Thomas Mueller called on fans to "stick together for one more week".
Writing on Instagram, Mueller -- who has won the last ten Bundesliga titles in a row with Bayern -- told his 12.8 million Instagram followers "everything is still possible".
Further down the pecking order, one of Union Berlin or Freiburg will join RB Leipzig in the Champions League for the first time.
Level on points, Union hold a slight advantage on goal difference and can all but secure a top four spot by beating Werder Bremen at home, where they have not lost a league match this season.
Union manager Urs Fischer said "there's a lot at stake in this game" but urged his side to "stay relaxed, otherwise we'll cramp up."
Guaranteed at least fifth and a spot in the Europa League, Freiburg face a slightly tougher task if they want to overtake Union and claim a first Champions League appearance, travelling to Eintracht Frankfurt.
Despite lifting the Europa League trophy almost exactly 12 months ago, Frankfurt have only a slight mathematical chance of a return to European football, needing a big win while hoping both Wolfsburg and Bayer Leverkusen lose.
At the other end of the table, while last-placed Hertha Berlin's return to the second division after a decade was sealed last week, any one of four clubs -- Schalke, Bochum, Stuttgart and Augsburg -- could join them.
Schalke likely have the toughest challenge, travelling to face RB Leipzig, while Bochum host Leverkusen and Augsburg visit Borussia Moenchengladbach.
The third-last side escapes the automatic trapdoor to the second division but must play a relegation playoff against the third-best side in the second division over a two-legged tie.
One to watch: Jude Bellingham (Borussia Dortmund)
Borussia Dortmund midfielder Jude Bellingham is in a race against time to be fit for Saturday's title-defining match against Mainz, in what may be his last game for the club.
Bellingham missed Dortmund's 3-0 win away at Augsburg on Sunday with a knee issue, only the second game the teenager has missed in the past two seasons due to injury.
Despite a contract which runs until 2025 at Dortmund, the 19-year-old is being courted by Real Madrid and Manchester City.
"I feel good" Bellingham said on social media on Wednesday, but sporting director Sebastian Kehl revealed the midfielder was sticking to an "incredibly ambitious" regime to return to the pitch.
Manager Edin Terzic said on Thursday Bellingham would "definitely be in the squad" but was still working hard to make the starting XI.
"We hope that the diligence he has shown will be rewarded."
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