Born on Sept. 18, 1961 in Westwood, N.J., Gandolfini cultivated an interest in theater while he was still in high school, and then went on to study communications at Rutgers University.
There, he met celebrity chef Mario Batali, who became a lifelong friend.
"I am totally shocked and devastated by the passing of one of my oldest and dearest friends," Batali told ABC News. "I only hope to help his family any way I can in their grief and mourning."
Gandolfini is survived by his wife, Deborah Lin, his daughter Liliana, 8 months, and his son, Michael, from a previous marriage.
After getting his start in the 1987 film "Shock! Shock! Shock!" Gandolfini went on to play a Virgil, a mob-enforcer in "True Romance" in 1993 and a lovable bodyguard in "Get Shorty," before landing the role of a lifetime, Tony Soprano, a few years later.
"I have lost a brother and a best friend," tweeted Steven Van Zandt, who co-starred with Gandolfini on "The Sopranos." "The world has lost one of the greatest actors of all time."
"Jimmy was a dear friend and like a brother to me. He was a great actor and a great father," said another of his "Sopranos" co-stars, Steve Schirripa. "I will miss him terribly. I am very sad."
ABC News' Anthony Castellano contributed to this report.