Captain Tom Moore, who won British hearts with a Covid-19 fundraising drive last year, on Tuesday died aged 100 after catching the virus, his family said.
They posted a picture of the charity hero with the words "Captain Sir Tom Moore 1920-2021" on his official Twitter page.
His daughters Hannah Ingram-Moore and Lucy Teixeira said in a statement that they were "so grateful that we were with him during the last hours of his life".
"We spent hours chatting to him, reminiscing about our childhood and our wonderful mother. We shared laughter and tears together.
"The last year of our father's life was nothing short of remarkable. He was rejuvenated and experienced things he'd only ever dreamed of," they added.
Queen Elizabeth II, who knighted Moore in July, will send a private message of condolence to his family, Buckingham Palace said.
Health Secretary Matt Hancock tweeted: "I'm so sorry to hear that Captain Tom has passed away in hospital.
"He was a great British hero that showed the best of our country & I send my best wishes to his family at this time."
Moore raised millions of pounds for the National Health Service (NHS) by walking around his garden and then became the oldest man to top the UK music charts with a cover of "You'll Never Walk Alone".
He was admitted to hospital in Bedford, central England, on Sunday having been treated over the past few weeks for pneumonia before testing positive for Covid-19 last month.
Liz Lees, chief nurse of the local NHS Trust, said it had been "our immense privilege to care for Captain Sir Tom Moore" and paid tribute to him for "the remarkable contribution he has made to the NHS".