Williams, 63, was found in the home he shared with his wife shortly before noon (3 p.m. ET), the Sheriff's Office said. He had last been seen alive on Sunday at 10 p.m., according to a Sheriff's Office press release.
"This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings," his wife, Susan Schneider, said in a statement. "I am utterly heartbroken. 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."
The comedian's publicist said he had been battling "severe depression of late."
"This is a tragic and sudden loss," Mara Buxbaum said in a statement. "The family respectfully asks for their privacy as they grieve during this very difficult time."
Williams, who struggled with alcohol and cocaine addiction was sober for decades but relapsed in 2006 and returned to rehab. Last month, Williams entered rehab for a short stay "to fine-tune and focus on his continued commitment, of which he remains extremely proud," according to a statements his representative made at the time.
In an interview with The Guardian in 2010, Williams attributed his need to self-medicate to his unrelenting "fear and anxiety" and said that although he was in a happier place, also was "not afraid to be unhappy. That's OK too. And then you can be like, all is good. And that is the thing, that is the gift."
The fast-talking comedian last communicated on social media two weeks ago when he shared a photograph of his daughter as a baby on her 25th birthday. A passionate gamer, Williams named his daughter Zelda.
Williams first came to prominence in 1978 as a naively sweet and zany alien in "Mork & Mindy," playing a character he'd originated in an episode of "Happy Days" with actress Pamela Dawber as his love interest. Dawber and Williams were reunited last year on CBS' "The Crazy Ones," when Williams returned to the medium that made him a star, playing an ad executive and father to a character played by Sarah Michelle Gellar.
“I am completely and totally devastated. What more can be said?!” Dawber said in a statement Monday.
“Our world has lost a comic genius, a gifted actor and a beautiful man," CBS said in a statement. "We will remember Robin Williams as one of the unique talents of his time who was loved by many, but also as a kind, caring soul, who treated his colleagues and co-workers with great affection and respect. Our heartfelt thoughts and sympathies go out to his family, loved ones and friends.”
Williams, who was as successful in stand-up as he was in TV and the movies, won an Academy Award for Best Supporting Actor for his role as Dr. Sean Maguire in the 1997 film "Good Will Hunting." He was nominated for Best Actor for his roles as an authority-bucking deejay in 1987's "Good Morning, Vietnam," as an inspirational teacher in 1989's "Dead Poets Society" (1989) and as a homeless man seeking the Holy Grail in 1991's "The Fisher King."
Williams also spearheaded the non-profit Comic Relief — concerts and variety shows — to raise money to help the homeless with Billy Crystal and Whoopi Goldberg. San Francisco Mayor Edwin M. Lee issued a statement saying the city was mourning a man who inspired with his comedy and his art.
His legacy has had a deep and inspiring impact on our City and on our residents," Lee said. "His ties to San Francisco were deep, having found early success in our city’s comedy clubs with his popular stand-up routines and where he was destined to launch a successful career that included starring roles in classic television shows and big screen success including an Academy Award. Despite his success, he has never forgotten San Francisco. He was a philanthropist who gave generously, and he was a friend of the City. San Francisco is heartbroken by the tragic loss of Robin Williams who forever changed the world with laughter and joy. Our thoughts and prayers are with his family and friends at this time of mourning.”
In April, Williams was reported to be planning to star in a sequel to his 1993 smash hit movie "Mrs. Doubtfire." News of Williams' unexpected death shook up William's close friends and the Hollywood entertainment community. When he appeared at a press event for his CBS comedy last year, Williams was in the wacky, frenetic state he was known for. All a journalist had to do was mention "sad clown" in a sentence and he was off: “Sad clown? What are those big feet doing in the bed!” he joked. “Wait, I’m getting a text from Carlos (Danger). Even the phone says no more!”
Flowers will be placed on Williams' star on the Hollywood Walk of Fame on Tuesday morning, the Hollywood Chamber of Commerce said.
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