Ken Sunshine says Harry -- who burst onto music charts in the 1950s before becoming a successful actor -- died Tuesday at his home in Manhattan of congestive heart failure.

Belafonte popularized calypso music in America in the early 50s with his infectious -- still, to this day -- hit song, "Banana Boat Song" ... also known as "Day-O." Younger folks will recognize it as that song from "Beetlejuice."

Harry was born in NYC to Jamaican-born parents, so his music was fueled by Caribbean sounds ... and his breakthrough album, "Calypso" became the first ever record to sell more than 1 million copies in a single year.

His music success made him in a commodity in Hollywood where he immediately landed roles in "Carmen Jones," "Island in the Sun" and "Odds Against Tomorrow." He was also very good friends with Sidney Poitier, with whom he costarred in the 70s classics, "Uptown Saturday Night" and "Buck and the Preacher."

As prominent as he was as an entertainer, Belafonte is equally hailed for his work as a civil rights leader and human rights activist. He was commonly seen marching with Dr. Martin Luther King Jr. in the 60s ... and he was at the forefront of efforts to fight famine in Africa.

He was one of the key organizers of the "We Are the World" charity record in 1985. In fact, Harry was so respected among the packed room of superstars that during the late night recording, they all spontaneously burst into a few verses of "Day-O." Very cool moment.

Just last December -- the last time he attended a public event -- he received the National Order of the Legion of Honour from the French government.

He's survived by his wife Pamela, 4 children -- including actress, Shari Belafonte -- 2 stepchildren and several grandchildren.

Harry Belafonte was 96.