His death is currently under investigation, though authorities suspect the actor may have taken his own life.
"Robin Williams passed away this morning. He has been battling severe depression of late," his representative said in a statement.
"This is a tragic and sudden loss. The family respectfully asks for their privacy as they grieve during this very difficult time."
His wife of nearly three years, Susan Schneider, released the following statement to the New York Times:
"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. 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 that the focus will not be on Robin's death but on the countless moments of joy and laughter he gave to millions."
The Mrs Doubtfire star checked into rehab in June to help him maintain his sobriety, his spokesperson said at the time.
The comedian, who has been candid about his battle with alcohol and substance abuse in the past, checked into a treatment facility to "focus on his commitment" to overcome his addictions.
"After working back-to-back projects, Robin is simply taking the opportunity to fine-tune and focus on his continued commitment, of which he remains extremely proud," his rep said.
Robin began his career as a stand-up comedian, but went on to become a celebrated film actor who excelled in both comedic and dramatic roles. Some of his most memorable films include Mrs. Doubtfire, Jumanji, Aladdin and Hook.
In 1998, Robin won an Academy Award for Best Supporting Actor for his role in Good Will Hunting.
He is survived by his three children: Zachary Pym, 31, Zelda Rae, 25, and 23-year-old Cody Alan Williams.