Lady Gaga has cancelled the last 10 dates of the European leg of her world tour due to "severe pain".
In a statement posted on Twitter, the pop star apologised to fans and said she was "devastated", but needed to put "myself and my well-being" first.
The Grammy award-winning singer has fibromyalgia, a long-term condition which can cause pain all over the body.
Shows in London and Manchester are among those affected.
In the statement, it said the "tough decision" had been made on Friday night with "strong support from her medical team".
Ticket holders can apply for a refund from 6 February, the statement added.
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"I'm so devastated I don't know how to describe it," Lady Gaga, 31, wrote. "All I know is that if I don't do this, I am not standing by the words or meaning of my music."
The announcement comes after she started the UK leg of her tour at Birmingham Arena.
Watching one of those performances, BBC arts editor Will Gompertz noted "the physicality of her performance compromised her singing at times".
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The European leg of her Joanne World Tour had already been rescheduled due to her condition and followed a decision to pull out of a performance at Rock In Rio in Brazil in September, after she was hospitalised with "severe physical pain."
The Born This Way singer was due to perform in Zurich, Cologne, Stockholm, Copenhagen, Paris and Berlin in the coming weeks.
At the end of last year, the star announced a two-year residency in Las Vegas, starting late in 2018.
What is Fibromyalgia?
- Fibromyalgia syndrome (FMS), is a long-term condition that causes pain all over the body
- People who suffer from it may also have difficulty sleeping, increased sensitivity to pain, fatigue and muscle stiffness
- The exact causes are unknown, although it can be triggered by physically or emotionally stressful events
- There is currently no cure for the condition
Her fans - who call themselves monsters - have been sending her messages of support on social media.
But many are disappointed.
Alice Outten had bought tickets for a London show as a birthday treat.
"I have train tickets and hotels booked in London," the 23-year-old, from Llandudno, said.
"I love Lady Gaga - she has been my idol for over 10 years, but this is just such a disappointment when I've been saving and saving to afford this trip and I was so excited."
Robert Miller, from Derby, has also been left out of pocket.
"My husband originally bought me tickets for us both to go for my birthday for the date in London last year costing £150 each," he said.
"We'd booked hotels and travel for then and couldn't cancel. It's happened again and we've been left with yet another costly trip to London for nothing."