Mansfield's Football League status is hanging by a thread after Rotherham substitute Jamie Yates netted a freak goal to give the Millers victory.
The Stags will be relegated on Tuesday if Chester draw with Stockport.
Mickey Boulding and Nathan Arnold forced saves from Andy Warrington, while United's Tom Cahill was twice denied by keeper Jason White.
Then Yates' effort, over 40 yards from goal, somehow dropped in underneath the crossbar and over the horrified White.
Furious Stags fans tried to storm the boardroom to get at owner Keith Haslam as the final whistle brought furious scenes on the pitch and in the stand.
Stags now face an uncertain week with their League future uncertain, while Rotherham's very existence continues to be in the balance.
Mansfield: White, Jelleyman, Buxton, Mullins, Briggs, Arnold, Dawson, D'Laryea, Hamshaw, Michael Boulding, Louis (Brown 67). Subs Not Used: Muggleton, Martin, Wood, Horlock.
Booked: Dawson, Briggs.
Rotherham: Warrington, Coughlan, Mills, Joseph, Green, Peter Holmes, Hudson, Danny Harrison, Tonge, Taylor (Derek Holmes 46), Cahill (Yates 55).
Subs Not Used: Newsham, Oxley, Ross.
Booked: Cahill, Taylor.
Goals: Yates 71.
Att: 5,271
Ref: Iain Williamson (Berkshire).
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