"This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings. I am utterly heartbroken," said Williams' wife, Susan Schneider.
"On behalf of Robin's family, we are asking for privacy during our time of profound grief. As he is remembered, it is our hope the focus will not be on Robin's death, but on the countless moments of joy and laughter he gave to millions."
Williams had been battling severe depression recently, said Mara Buxbaum, his press representative.
Video: Comedian Robin Williams found dead
Obama: Williams was 'one of a kind'
US President Barack Obama and the US first family joined a national outpouring of grief to pay tribute to the deceased actor and comedian Robin Williams.
"Robin Williams was an airman, a doctor, a genie, a nanny, a president, a professor, a bangarang Peter Pan, and everything in between. But he was one of a kind, " Obama said.
"He arrived in our lives as an alien - but he ended up touching every element of the human spirit," Obama added, referring to Williams' breakthrough television role as the extra-terrestrial visitor Mork.
"He made us laugh. He made us cry. He gave his immeasurable talent freely and generously to those who needed it most - from our troops stationed abroad to the marginalised on our own streets. The Obama family offers our condolences to Robin's family, his friends, and everyone who found their voice and their verse thanks to Robin Williams," the statement concluded.
The marquee of the Laugh Factory shows a message in memory of Williams. Photo / AP
Robin Williams performing at a Stand Up For Heroes benefit concert. Photo / AP
Jonah Lomu: 'We sure had a lot of laughs together'
Former All Black Jonah Lomu wrote a heartfelt tribute to his friend on his website: "My friend, it's sad to hear of your passing, it was an honour and privilege to have known you, we sure had a lot of laughs together. I still remember the first time we met, it feels like yesterday but we have both grown up a little more since then, our times were full of laughs.
"Our thoughts are with your friends and family at this time and there is a world of us that will miss you my friend. Till we meet again for more laughs, your friends Jonah and Nadene Lomu."
Robin Williams (2nd L), with at the 70th Annual Academy Awards in 1998. Photo / AP
New Zealand Academy Award winner and film maker Vincent Ward became friends with Williams during the shooting of his 1998 film What Dreams May Come.
"Even if for a moment you forget this man's extraordinary talent and wicked humour, if you have worked with him you know one thing - what a wonderful, extraordinary and kind man he was," said Ward, a University of Canterbury adjunct professor.
Robin Williams performs at the Vector arena, Auckland. Photo / Michael Craig
From his breakthrough in the late 1970s as the alien in the hit TV show Mork and Mindy, through his standup act and such films as Good Morning, Vietnam, the short, barrel-chested Williams ranted and shouted as if just sprung from solitary confinement. Loud, fast, manic, he parodied everyone from John Wayne to Keith Richards, impersonating a Russian immigrant as easily as a pack of Nazi attack dogs.
He was a riot in drag in Mrs Doubtfire, or as a cartoon genie in Aladdin. He won his Academy Award in a rare, but equally intense dramatic role, as a teacher in the 1997 film Good Will Hunting.
Robin Williams pictured as Mrs Doubtfire.
He was no less on fire in interviews. During a 1989 chat with The Associated Press, he could barely stay seated in his hotel room, or even mention the film he was supposed to promote, as he free-associated about comedy and the cosmos.
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"There's an Ice Age coming," he said. "But the good news is there'll be daiquiris for everyone and the Ice Capades will be everywhere. The lobster will keep for at least 100 years, that's the good news. The Swanson dinners will last a whole millennium. The bad news is the house will basically be in Arkansas."
Billy Crystal and Robin Williams together in the movie 'Father's Day'.
Following Williams on stage, Billy Crystal once observed, was like trying to top the Civil War. In a 1993 interview with the AP, Williams recalled an appearance early in his career on The Tonight Show Starring Johnny Carson. Bob Hope was also there.
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"It was interesting," Williams said. "He was supposed to go on before me and I was supposed to follow him, and I had to go on before him because he was late. I don't think that made him happy. I don't think he was angry, but I don't think he was pleased.
"I had been on the road and I came out, you know, gassed, and I killed and had a great time. Hope comes out and Johnny leans over and says, 'Robin Williams, isn't he funny?' Hope says, 'Yeah, he's wild. But you know, Johnny, it's great to be back here with you.'"
In 1992, Carson chose Williams and Bette Midler as his final guests.
Serious ambitions
Like so many funnymen, he had serious ambitions, winning his Oscar for his portrayal of an empathetic therapist in Good Will Hunting. He also played for tears in Awakenings, Dead Poets Society and What Dreams May Come, something that led New York Times critic Stephen Holden to once say he dreaded seeing the actor's "Humpty Dumpty grin and crinkly moist eyes."
Robin Williams holding his Oscar high backstage at the 70th Academy Awards in 1998. Photo / AP
Williams also won three Golden Globes, for Good Morning, Vietnam, Mrs. Doubtfire and The Fisher King.
His other film credits included Robert Altman's Popeye (a box office bomb), Paul Mazursky's Moscow on the Hudson, Steven Spielberg's Hook and Woody Allen's Deconstructing Harry. On stage, Williams joined fellow comedian Steve Martin in a 1988 Broadway revival of Waiting for Godot.
"I dread the word 'art,'" Williams told the AP in 1989. "That's what we used to do every night before we'd go on with 'Waiting for Godot.' We'd go, 'No art. Art dies tonight.' We'd try to give it a life, instead of making "Godot" so serious. It's cosmic vaudeville staged by the Marquis de Sade."
Personal life often short on laughter
His personal life was often short on laughter. He had acknowledged drug and alcohol problems in the 1970s and '80s and was among the last to see John Belushi before the Saturday Night Live star died of a drug overdose in 1982.
Williams announced in recent years that he was again drinking but rebounded well enough to joke about it during his recent tour. "I went to rehab in wine country," he said, "to keep my options open."
Robin Williams in the film 'The World According to Garp'. Photo / AP
Early years
Born in Chicago in 1951, Williams would remember himself as a shy kid who got some early laughs from his mother - by mimicking his grandmother. He opened up more in high school when he joined the drama club and he was accepted into the Juilliard Academy, where he had several classes in which he and Christopher Reeve were the only students and John Houseman was the teacher.
Encouraged by Houseman to pursue comedy, Williams identified with the wildest and angriest of performers: Jonathan Winters, Lenny Bruce, Richard Pryor, George Carlin. Their acts were not warm and lovable. They were just being themselves.
"You look at the world and see how scary it can be sometimes and still try to deal with the fear," he told the AP in 1989. "Comedy can deal with the fear and still not paralyze you or tell you that it's going away. You say, OK, you got certain choices here, you can laugh at them and then once you've laughed at them and you have expunged the demon, now you can deal with them. That's what I do when I do my act."
Robin Williams on the set of 'Mork and Mindy'. Photo / AP
He unveiled Mork, the alien from the planet Ork, in an appearance on Happy Days, and was granted his own series, which ran from 1978-82.
In subsequent years, Williams often returned to television - for appearances on Saturday Night Live, for Friends, for comedy specials, for American Idol, where in 2008 he pretended to be a Russian idol who belts out a tuneless, indecipherable My Way.
Ad-libbing master
Williams also could handle a script, when he felt like it, and also think on his feet. He ad-libbed in many of his films and was just as quick in person. During a media tour for Awakenings, when director Penny Marshall mistakenly described the film as being set in a "menstrual hospital," instead of "mental hospital," Williams quickly stepped in and joked, "It's a period piece."
Winner of a Grammy in 2003 for best spoken comedy album, , Robin Williams - Live 2002, he once likened his act to the daily jogs he took across the Golden Gate Bridge. There were times he would look over the edge, one side of him pulling back in fear, the other insisting he could fly.
"You have an internal critic, an internal drive that says, 'OK, you can do more.' Maybe that's what keeps you going," Williams said. "Maybe that's a demon. ... Some people say, `It's a muse.' No, it's not a muse! It's a demon! DO IT YOU BASTARD!! HAHAHAHAHAHAHA!!! THE LITTLE DEMON!!"
Robin Williams' hand and footprint impression at the TCL Chinese Theatre in LA. Photo / Getty Images/AFP
Tributes are flowing for Robin Williams on Twitter:
I could not be more stunned by the loss of Robin Williams, mensch, great talent, acting partner, genuine soul.
Robin Williams made the world a little bit better. RIP.
No matter what people tell you, words and ideas can change the world." - Robin Williams
A beautiful shot of Robin Williams on arrival in Auckland - Dec 22, 1999 @nzherald pic.twitter.com/WajOVcjir7
No words can express the sadness I feel for this tragic loss. My prayers are with the Williams family. RIP Robin Williams. -ZS
Where to get help
• Lifeline: 0800 543 534
• Suicide Crisis Helpline: 0508 828 865
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• The Word
• Depression helpline: 0800 111 757 (24-hour service)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
- AFP, AP, APNZ, nzherald.co.nz
