Veteran actor Sir Antony Sher has died of cancer aged 72, the Royal Shakespeare Company (RSC) has announced.
He was widely regarded as one of the country's finest contemporary classical actors, with a long association with the company.
Its artistic director and Sir Antony's husband, Gregory Doran, had taken compassionate leave to care for him.
The company said it was "deeply saddened" by the news.
RSC chair Shriti Vadera said the actor was "beloved" in the organisation "and touched and enriched the lives of so many people".
"Our thoughts and sincere condolences are with Greg, and with Antony's family and their friends at this devastating time," added Catherine Mallyon, RSC executive director and Erica Whyman, acting artistic director.
Sir Antony's film appearances included Shakespeare in Love and Mrs Brown, while his RSC credits included Richard III and Macbeth. He also appeared in TV series including The History Man and the BBC's Murphy's Law.
Once described by the Prince of Wales as his favourite actor, Sir Antony played many of the great Shakespearean roles, from King Lear to Shylock.
But it was his portrayal of Richard III as a villainous hunchback on crutches which won him an Olivier Award in 1985.
Prince Charles, who is president of the Royal Shakespeare Company, said he was "deeply saddened" by the death of Sir Antony, who he described as "a great man and an irreplaceable talent".
"I had the great joy and privilege of knowing him for many years, and admired him enormously for the consummate skill and passion he brought to every role," Prince Charles said.
"My most treasured memory of him was as Falstaff in a brilliant production of Greg Doran's.
"I feel particularly blessed to have known him, but we have all lost a giant of the stage at the height of his genius."
Actor John Simm paid tribute on Instagram, sharing a memorable image of the Sir Antony as Richard III, while describing him as "one of the greatest stage actors I've ever seen."
Simm described Sir Antony as "a huge inspiration, a huge talent".
Screenwriter and producer Russell T Davies, who created It's A Sin, commented: "He's a wonderful man," while the National Theatre added: "With the tragic passing of Antony Sher, one of the great theatre titans has left us."
Writing on Twitter, choreographer Sir Matthew Bourne said: "Terribly sad… My thoughts are with Greg and everyone who loved Sir Antony - a truly great loss."
Actor Samuel West said in a Twitter thread tribute that so many of his performances "stay with me after decades - Macbeth, Stanley, Arturo Ui, Torch Song Trilogy, Cyrano - and today people are remembering dozens of others, in every genre and style. The mark of a true artist".
Singer Gary Kemp, of Spandau Ballet, said some of his "most powerful theatre-viewing experiences" had occurred while watching Sir Antony.
South African-raised Sir Antony joined the RSC in 1982.
In his early teens he had elocution classes, which helped him to overcome the shyness he had felt as a boy.
But he almost gave up on his acting career after an early rejection from the Royal Academy of Dramatic Art (Rada) in London.
"That was my beginning in this country and I took the rejections very seriously," he told The Telegraph in 2018,
"I assumed the examiners knew best, but my mother, who was a very ambitious Jewish woman, was absolutely determined that they were wrong and kept me going. I honestly think I would have given up if it weren't for her."
'Never went to university'
Sir Antony became an honorary associate artist with the RSC, based in Stratford-upon-Avon in Warwickshire.
In 2010, he told the BBC about his first visit there and described it as one of the most significant experiences of his life.
Five years later, he took issue with Downton Abbey creator Julian Fellowes' opinion that one needed a university education to properly understand Shakespeare.
"I am sorry, that is nonsense," said Sir Antony in an interview with the BBC's Sue MacGregor.
"I never went to university but my job as a Shakespeare actor - and I have done a lot of them now - is to work hard on conveying the meaning."
He added: "It's not a university degree you need, it's the craft of speaking Shakespeare, which we at the RSC work very hard at."
Sir Antony was knighted in 2000, and in 2005, with Mr Doran, who he met at the RSC, became one of the first gay couples to enter into a civil partnership in the UK.
The RSC said Doran will remain on compassionate leave and is expected to return to work in 2022.
Fellow actor and playwright John Kani said in a tribute: "Both Tony Sher and I were born when our country, South Africa, was the worst place a child could be born let alone to be raised by parents who worked very hard to prepare their children for a difficult future - Apartheid South Africa. By the grace of his God and my ancestors, like Romeo and Juliet we found each other in 1973.
"We travelled together as compatriots, comrades in the struggle for a better South Africa, as fellow artists... I am at peace with you my friend and myself. Exit my King. Your Brother."