His family confirmed the very sad news in a statement on Saturday (20 February).
Paul, who came to fame as a much-loved TV magician in the 80s and 90s, is married to Debbie McGee, 57 - his glamorous onscreen assistant.
A statement on Paul's official website said: "We can confirm that one of our greatest magicians and entertainers of all times, Paul Daniels, has sadly been diagnosed with an incurable brain tumour.
"On behalf of Paul, Debbie and their families, we thank you for your kind concerns and support at this sad time and ask that their privacy continues to be respected.
"There will no further comments at this time."
Wife Debbie also posted the link to the statement, with the words: "With great sadness."
Paul is currently in the middle of a UK tour called the Intimate Magic Show.
However this month he has been forced to pull out of a number of shows.
The veteran entertainer burst onto our TV screens in 1970 when he came second on the talent series Opportunity Knocks.
He later got his own primetime series, The Paul Daniels Magic Show, which was shown on the BBC between 1979-1994 and was one of the most popular shows at that time.
Debbie performed as an assistant alongside Paul. The couple married in 1988 and have been happily married ever since.
With great sadness https://t.co/UX8lnuFYBK— Debbie McGee (@thedebbiemcgee) February 20, 2016
They have often appeared on TV together, and featured on C4's Celebrity Wife Swap - where Paul swapped spouses with Vanessa Feltz.
Paul, whose real name is Newton Edward Daniels, appeared as a contestant on BBC's Strictly Come Dancing in 2010.
He was paired with Ola Jordan, and was the second celebrity to be voted off.
Paul is well known for his "You'll like this ... not a lot, but you'll like it" catchphrase.
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