His death was announced by his movie star son Michael Douglas.
A statement shared on Instagram by Michael read: "It is with tremendous sadness that my brothers and I announce that Kirk Douglas left us today at the age of 103.
"To the world, he was a legend, an actor from the golden age of movies who lived well into his golden years, a humanitarian whose commitment to justice and the causes he believed in set a standard for all of us to aspire to.
"But to me and my brothers Joel and Peter he was simply Dad, to Catherine, a wonderful father-in-law, to his grandchildren and great-grandchild their loving grandfather, and to his wife Anne, a wonderful husband."
Michael, 75, continued: "Kirk’s life was well-lived, and he leaves a legacy in film that will endure for generations to come, and a history as a renowned philanthropist who worked to aid the public and bring peace to the planet.“Let me end with the words I told him on his last birthday and which will always remain true.
"Dad - I love you so much and I am so proud to be your son.”
Douglas was one of the last surviving stars of Hollywood's Golden Age and had a total of 92 acting credits - including in 75 movies - under his belt.
Michael's post sparked a flood of tributes from the world of show-business - including his movie star daughter-in-law Catherine Zeta Jones, 50.
The Welsh actress, who married Michael in 2000, paid tribute to "my darling Kirk".
Alongside a black-and-white picture showing her kissing him on the cheek, Zeta Jones wrote: "I shall love you for the rest of my life. I miss you already. Sleep tight..."
Revered director Steven Spielberg said Douglas left behind a "breathtaking body of work".He said: "Kirk retained his movie star charisma right to the end of his wonderful life and I'm honoured to have been a small part of his last 45 years.
"I will miss his handwritten notes, letters and fatherly advice, and his wisdom and courage - even beyond such a breathtaking body of work - are enough to inspire me for the rest of mine."
Star Wars actor Mark Hamill called Douglas "one of the biggest stars of all time & a brilliant actor with an unforgettable, blazing charisma."
He added one of Douglas's greatest achievements was rebelling against the Hollywood blacklist of alleged Communists and sympathisers during the Cold War era.
"He will also be remembered for putting his career on the line by defying the Hollywood Blacklist, hiring writer Dalton Trumbo for the classic Spartacus," Hamill said.
Star Trek actor William Shatner paid his respects to Douglas' family."Condolences to the family of Kirk Douglas. What an incredible icon he was in this industry!," Shatner said.
Actor Danny DeVito was upbeat in his reflection of Douglas' career, tweeting: "Kirk Douglas. The inspirational Scalawag.
"103 years on this earth. That's got a nice ring to it! Great hanging with you man."
Kirk's grandson Cameron was also seen on Wednesday evening leaving the Beverly Hills home where his legendary grandfather had passed away hours earlier.
Joel Douglas, Kirk's son, also left the home on Wednesday evening as emotional fans gathered at Kirk's star on the Hollywood Walk Of Fame to leave floral tributes.
Kirk was born Issur Danielovitch in New York, and his dad was a rag-and-bone man of Russian-Jewish ancestry.
He put a fledgling Broadway career on hold to enlist in the US Navy in 1941 but after World War Two he went on to star in more than 90 films over seven decades.
Famously, he once earned £38,000 for saying the only English word — “coffee” — at the end of a 1980s Japanese TV advert.
In the 1950s and 1960s he was part of a small group of artists who helped to break the Hollywood blacklist.
It saw the denial of employment to actors, screenwriters, directors, musicians, and others who were believed to be communist sympathizers.
But Kirk shunned the so-called "Red Scare" by hiring Dalton Trumbo -one of the "Hollywood Ten" who were suspected of harbouring pro-Soviet sympathies - to write Spartacus.
Off-screen, he served as a Goodwill Ambassador for the US State Department and received the Presidential Medal of Freedom from Jimmy Carter in 1981.
The actor was finally awarded an honorary Oscar for 50 years in the industry in 1996.
Kirk had spent the last few decades of his life refocusing his attention on spirituality and Judaism after he was a lucky survivor of a helicopter crash in 1991 and then later a stroke in 1996.
He married his first wife Diana in 1943 and the pair welcomed two sons, actor Michael Douglas and producer Joel Douglas.
They divorced in 1951 and he married Anne Buydens in 1954 after they met on the set of Lust For Life.
Kirk and Anne had two sons, Peter, a producer, and Eric, an actor who sadly died on July 6, 2004, from an overdose.
Douglas received his first Academy Award nomination in 1949 for Champion and was nominated again in 1952 for The Bad And The Beautiful and 1956 in Lust For Life.
But it was in 1960 that he took on his most iconic role in the Hollywood classic Spartacus, where he played the gladiator leader.
Kirk was the star and executive producer - while the film was directed by legendary filmmaker Stanley Kubrick.
The phrase "I'm Spartacus!" has gone on to become a cultural reference point, and was used over and over in the decades since in other films, television programs, and adverts.