The actor was 103-years-old.

Kirk Douglas, who had a six-decade-long acting career and is the father of famous actor Michael Douglas, has died at the age of 103.

Michael posted a heartfelt message on his Instagram page today:

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.

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.

What's your favorite Kirk Douglas movie? I've always loved Tough Guys.