Madrid needed the victory to keep Barcelona from clinching their 28th league title in advance. The Catalan club remain four points ahead and can still lift the trophy with a win at city rivals Espanyol on Thursday.
Elsewhere on Wednesday night, there were also home wins for Villarreal and Alaves.
Villarreal consolidated fifth with a 3-0 victory over Leganes, who are four points from safety in 18th with just two rounds remaining, while 17th-placed Alaves triumphed 1-0 at mid-table Valencia.
In the capital, Mallorca took the lead with a goal by Martin Valjent in the 11th minute and stayed ahead until Kylian Mbappe beat a couple of defenders to equalise in the 68th.
Ramon netted the go-ahead goal from inside the area in the 95th to keep Barcelona from winning the La Liga title.
Mbappe is still in the race to be the league's leading scorer, arriving at the Santiago Bernabeu with 27 goals, two more than Barcelona's Robert Lewandowski.
Barcelona virtually secured the title by coming from behind to beat Madrid 4-3 in Barcelona in the last "clasico" of the season on Sunday.
Madrid lost all four matches against Barca this season, being outscored 16-7. It was the first time Barcelona won every "clasico" in a season that had at least three matches between the rivals.
Madrid coach Carlo Ancelotti received a mostly indifferent reaction from the fans after taking over the Brazil job.
Ancelotti was announced as Brazil's new coach on Monday, and some Madrid fans criticised the Italian for negotiating with the five-time world champions with the season still underway.
There were no significant jeers or cheers when his name was announced by the loudspeakers before the match, with most fans applauding and saying his name along with the announcer, following the tradition at the stadium.
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