Nikki Grahame has died at the age of 38.
Nikki took part in the seventh series in 2006 and was one of the show's most recognisable stars.
She returned as a housemate in UK Big Brother twice: in Ultimate Big Brother in 2010 and also the 2015 series. In 2016 she took part in the Canadian version of the show.
Nikki battled with anorexia for many years, and she released a book in 2009.
Last month, a fundraising page was set up, asking fans to donate towards her recovery.
The page said the 38-year-old was in "a very bad way" and needed treatment in a rehabilitation centre.
The page has been updated with following message.
It is with great sadness, we have to let you know that our dear friend Nikki passed away in the early hours of Friday 9th April.
It breaks our hearts to know that someone who is so precious was taken from us at such a young age. Nikki not only touched the lives of millions of people, but also her friends and family who will miss her immensely.
We would like to request privacy at this difficult time, while Nikki's friends and family process the sad news.
Full details will be released as and when we know them.
All donations have been greatly appreciated and it was heartwarming for everyone including Nikki to see how much she was loved.
Funds will be held safely in this GoFundMe until we have established an organisation supporting those suffering from anorexia to which we will make a donation in Nikki's memory. We will post updates for you with more details as soon as we have them.
We are working with GoFundMe at this time. If you want to request a refund, you can write into GoFundMe's team here:
Rest In Peace, Nikki. We love you & not a day will go by without missing your smile. X X X
Davina McCall wrote in tribute on Twitter: "I am so desperately sad to hear about Nikki Grahame. My thoughts are with her friends and family xx she really was the funniest, most bubbly sweetest girl."
Marcus Bentley posted "‘Who is she’? The best housemate ever! Night, night Princess Nikki!".
Rylan Clark-Neal wrote "Thinking of Susan and Nikki’s close friends and family. A Big Brother Icon x"