Veteran Labour MP Dennis Skinner has lost the Bolsover seat he has held for 49 years.
The 87-year-old was beaten by Conservative candidate Mark Fletcher by 5,299 votes.
Skinner - nicknamed the Beast of Bolsover - had been defending a majority of 5,288 achieved in 2017.
The former miner and prominent ally of party leader Jeremy Corbyn was not at the count when the result was announced.
During his five decades in Parliament, Skinner earned a reputation for his sharp tongue and straight-talking style.
In recent years he regularly interrupted the State Opening of Parliament with a topical heckle.
The BBC's Jeremy Vine said Bolsover was the result that took the Conservatives over the line to confirm their emphatic election victory.
New MP Mr Fletcher paid tribute to Mr Skinner in his victory speech, describing him as "a wonderful constituency MP" who had "inspired millions of people".
"I'm very sad he can't be here because I haven't found a street in this constituency where Dennis hasn't helped somebody."
If you can't see the graphic click here.
Elsewhere in Derbyshire, Labour's Ruth George lost her High Peak seat to Conservative Robert Largan.
But Dame Margaret Beckett retained Derby South with a reduced majority.
Conservative Amanda Solloway won back the Derby North seat she lost to Chris Williamson in 2017 prior to his Labour suspension.
Mr Williamson picked up 635 votes standing as an independent candidate in the same constituency.
Mid Derbyshire, Derbyshire Dales, Erewash, South Derbyshire, Amber Valley and North East Derbyshire were all held by the Conservatives, while Labour retained Chesterfield.
By Chris Doidge, BBC Derby political reporter
The Conservatives have greatly increased their hold on Derbyshire - largely through a sharp fall in Labour's share of the vote.
It's clear in the seats that wanted Brexit the most, the Conservatives have performed well - Amber Valley, Bolsover and North East Derbyshire all swung sharply towards Boris Johnson's party.
But in the Derby seats, the Conservatives didn't pick up many more votes than in 2017 - Labour's disappearing voters instead went to other parties or didn't vote at all.
The Brexit Party performed poorly in the seats they stood in, despite claiming they were in with a chance of winning seats here.
And it was a disastrous result for Chris Williamson.
Has an incumbent ever gone from winning almost half the votes in one election, to picking up just 1.4% of the votes in the next one? His Parliamentary career is surely over.
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