He died of prostate cancer, according to the Associated Press citing a statement from his family released by Marcia Newberger, spokeswoman for The Griffin Group/Merv Griffin Entertainment.
Griffin, who was first diagnosed with prostate cancer in 1996, was being treated at Cedars-Sinai Medical Center in Los Angeles for a recurrence of the disease, it was reported on July 18.
A former band singer from San Mateo, Calif., Griffin – who as a chubby young man was nicknamed "Buddy" – had his first hit with the novelty song, "I've Got a Lovely Bunch of Coconuts."
His longtime TV career was launched in the '50s with variety-show appearances that eventually culminated in the 1965 launch of his syndicated Merv Griffin Show, versions of which ran until 1986.
During the '70s, he invented and produced the popular game shows Jeopardy! and Wheel of Fortune – which by 1986 made him a very rich man when he sold his company to Columbia Pictures Television for $250 million.
Wheel of Fortune host Pat Sajack issued the following statement on Sunday about Griffin: "The loss of a dear friend has made it difficult to focus on Merv's enormous contribution to the world of entertainment. That will come in time; for now, like his family and so many of his close friends, I'm dealing with deep sadness and the realization that I will never hear that wonderful laugh of his again. He meant so much to my life, and it's hard to imagine it without him."
After making his fortune in TV, Griffin invested in hotel and casino properties and became a magnate, even publicly battling Trump over some Atlantic City and Bahamas properties in the 1980s.
But it was his popular talk show that made him a household name and role model for such later hosts as Rosie O'Donnell (when she first had her talk show) and Ellen DeGeneres, whose easy-going styles and softball questions have often been likened to Griffin's.
Griffin, who was divorced from ex-wife Julann Griffin, is survived by a son, Tony Griffin, a daughter-in-law Tricia, and two grandchildren, Farah and Donovan Mervyn.
On his production company's Web site, which says he hosted 5,500 shows and interviewed more than 25,000 guests in more than 23 years, Merv Griffin is quoted as saying, "I'm a very lucky guy. My life is never boring. I treat my professional life the same way I do my personal life. And I measure success the same way – by how much fun I'm having, and by how much fun I'm creating around me."