England captain Harry Kane’s late goal at Bochum was not enough as Bayern Munich suffered their third defeat in nine days.
Bayern took the lead through Jamal Musiala, before the first of two stoppages following fans’ protests.
Bochum scored twice, with goals from Takuma Asano and Keven Schlotterbeck.
Kevin Stoger’s penalty made it 3-1 after Dayot Upamecano had been sent off and, despite Kane’s 25th league goal of the season, it was not enough.
Thomas Tuchel’s Bayern are now eight points behind Bundesliga leaders Bayer Leverkusen.
Tuchel said winning the Bundesliga title “does not look very realistic”, but added: “Last season we believed until the end and we were rewarded. So we will keep working at it.”
Bayern have been German champions in each of the past 11 seasons but now face the possibility of ending the campaign without a trophy.
They lost in the German Super Cup in August and then went out of the German Cup in the second round to third-tier Saarbrucken in November.
Tuchel’s side lost 3-0 at Leverkusen on 10 February and were then beaten 1-0 by Lazio in the first leg of their Champions League last-16 tie in midweek.
Referring to the pressure on him following his team’s third loss, Tuchel added: “That happens after every defeat.
“The ‘how’ we played is key. The ‘how’ was good and that’s why this 90 minutes are very different from the second half at Lazio or the game at Leverkusen.”
This defeat was the first time Bayern have lost three matches in a row since May 2015, when managed by Pep Guardiola.
More protests at Bundesliga games
Midway through the first half, and again early in the second, play was stopped for just under 10 minutes on each occasion following protests by the fans, in which tennis balls were thrown on to the pitch.
Protests are becoming a regular occurrence at Bundesliga matches with supporters unhappy with an investment proposal by the German Football Association.
In December, a majority vote by German clubs approved a proposal to sell some Bundesliga TV rights in exchange for investment capital and since then there has been a variety of protests.
On Saturday, the Bundesliga 2 match between Hansa Rostock and Hamburg was interrupted by remote control cars carrying smoke bombs.
Last week, tennis balls and chocolate gold coins were thrown on to the pitch by fans in the Borussia Dortmund section causing a 10-minute delay in their game against Freiburg.
On Friday, 9 February, there was a protest during a Hannover game when Hamburg fans chained six padlocks to a goal at half-time which had to be cut off before play could resume.
Kane continues to reach goalscoring landmarks
Bayern had scored first through Musiala’s powerful strike, but conceded twice in a five-minute spell after the first of the two stoppages.
Upamecano picked up his second yellow card and was dismissed after elbowing Schlotterbeck – his second sending-off in five days after being red-carded against Lazio – with Bochum converting the penalty to go 3-1 ahead.
Bundesliga top scorer Kane got a goal back late on but his side could not force an equaliser.
He did manage to set a new record as he became the quickest to reach 25 Bundesliga goals in one season, doing so in 22 games to beat the previous best mark of 25 by former Borussia Dortmund striker Erling Haaland.
Kane, who moved from Tottenham for £86.4m last summer, has not won a major trophy in his career, so will be hoping Bayern can catch Leverkusen and turn around their European deficit.
