The actor, who is believed to have died of a heart attack, was traveling in Italy at the time of his death Wednesday. HBO confirmed his death.
"We're all in shock and feeling immeasurable sadness at the loss of a beloved member of our family," an HBO statement said. "He was special man, a great talent, but more importantly a gentle and loving person who treated everyone no matter their title or position with equal respect. He touched so many of us over the years with his humor, his warmth and his humility. Our hearts go out to his wife and children during this terrible time. He will be deeply missed by all of us."
David Chase, creator of "The Sopranos," said in a statement: "He was a genius. Anyone who saw him even in the smallest of his performances knows that. He is one of the greatest actors of this or any time. A great deal of that genius resided in those sad eyes. I remember telling him many times, 'You don't get it. You're like Mozart.' There would be silence at the other end of the phone. For Deborah and Michael and Liliana this is crushing. And it's bad for the rest of the world. He wasn't easy sometimes. But he was my partner, he was my brother in ways I can't explain and never will be able to explain."
What made Gandolfini's work so special in the HBO drama that ran from 1999 to 2007 was the range of emotions he could scale in a single episode. Heck, in a single scene. He made the anti-hero both more lovable and frightening -- that is to say, more human and believable.
It was there in the pilot as he moved effortlessly from anxiety-ridden, sensitive suburban dad and husband fretting over the fate of a mother duck and her ducklings that had found a home in his McMansion's pool, to a savage mob collector running down and taking a baseball bat to the knees of a man who owed him money. The beating was one of the most vicious I had ever seen on TV.
The transformation was startling and frightening, and I can't think of three other actors in television who could have pulled it off, and made me believe. Gandolfini's acting was the reason I fell in love with the series.
But that range was never more on display than in fourth season with Tony's relationship with the race horse Pie-O-My. One unforgettable episode ends late at night with him sitting in the straw in a stable with the ailing horse as a storm rages outside. It is as existential and profoundly touching a moment of bonding between two creatures on this lonely planet as I have ever seen in the arts -- Samuel Beckett notwithstanding. Again, it was Gandolfini who made you believe this sometimes monster named Tony could be so tender, protective, empathetic and kind.
In a later episode, the beast within Tony was given full and frigtening play when he choked Ralph Cifaretto (Joe Pantoliano) to death in part for Cifaretto's sins against that horse. And somehow, Gandolfini made the killing seem both simultaneously righteous and depraved. As fine as the writing was on this series created by David Chase, that darkly transcendent scene was all about the acting.
Along with "The Wire," "The Sopranos" made cable TV -- not network or public television -- the centerstage of quality drama in American life. And no actor on either show played a larger role in making that happen than James Gandolfini.
Gandolfini, who won three Emmys for his work in "The Sopranos," was also an outstanding comic performer. His turn as a general in Armando Iannucci's feature film "In the Loop" was one of the great joys of the brilliant satire of British-American politics.
He also appeared in the feature films "Zero Dark Thirty," "Not Fade Away," "The Taking of Pelham 1 2 3" and "Killing Them Softly."
The New Jersey native was an executive producer of other projects for HBO: "Hemingway and Gellhorn," a made-for-TV movie, and "Alive Day Memories: Home From Iraq," a documentary on soldiers and Marines home from that war. In "Wartorn," another documentary he produced for HBO, Gandolfini explored the history and toll of post traumatic stress of those who fight America's wars.
"Jimmy treated us all like family with a generosity, loyalty and compassion that is rare in this world. Working with him was a pleasure and a privilege. I will be forever grateful having had a friend the likes of Jimmy," said Michael Imperioli, who played Tony's nephew, Christopher Moltisanti, in "The Sopranos."
"I am shocked and devastated by Jim's passing," said Edie Falco, who played Tony's wife, Carmela, in "The Sopranos." "He was a man of tremendous depth and sensitivity, with a kindness and generosity beyond words. I consider myself very lucky to have spent 10 years as his close colleague. My heart goes out to his family. As those of us in his pretend one hold on to the memories of our intense and beautiful time together. The love between Tony and Carmela was one of the greatest I've ever known."
Gandolfini is survived by his wife, Deborah, and a son and daughter.
Correction: An earlier version incorrectly described the instrument of Ralph's Cifaretto's death.