The law firm representing the composer said he died late Tuesday, without giving a cause of death.
In a post on Twitter, Greek Prime Minister Kyriakos Mitsotakis called Vangelis “a pioneer in electronic sound”.
“He began his long journey on the Chariots of Fire. From there he will always send us his bonds,” Mitsotakis wrote.
“Ad astra, Vangelis” – which means “to the stars” in Latin – NASA tweeted, saying Vangelis contributed scores to its explorations to Jupiter.
Born Evangelos Odysseas Papathanassiou in 1943, the young Vangelis took an early interest in music and experimented with the sounds produced by banging on pots or attaching nails, glasses and other objects to the strings of his parents’ piano.
He absorbed the sounds of Greek folksongs and Orthodox Christian choral music, but had no formal musical training, which he would later say helped save his sense of creativity.
After beginnings with local rock bands, Vangelis left for Paris at the age of 25, joining an exodus of young artists following the 1967 coup that installed a military junta in Greece.
Away from home, he was drawn to the then-new field of electronic synthesizers that allowed him to create the lush melodic colors that became his trademark.
Although he enjoyed success on the European “prog rock” scene in the early 1970s with Aphrodite’s Child, a band he formed with fellow Greek Demis Roussos, Vangelis was not comfortable with the expectations of a commercial artist and retired to his self-made recording studio in London.
It was there that he wrote the score for “Chariots of Fire”, the story of the triumph of a group of British runners at the 1924 Olympics.
Unashamed and uncontemporary, its pulsating synthesizer beats and soaring melody made the slow-motion opening sequence of a group of athletes running along a beach a model for how cinema represented sport. .
Vangelis once said that the score, which won him an Oscar and topped the charts for weeks, was in part a tribute to his father, who was an avid amateur runner. But he was also slightly dismissive of the enormous popularity she enjoyed.
“It’s just another piece of music,” he told an interviewer.
The success of “Chariots of Fire” clipped his other scores, but he wrote the music for several major films, including “Missing”, directed by fellow countryman Costa-Gavras, and Ridley Scott’s futuristic thriller “Blade Runner”.
He was a prolific composer for several decades, his work ranging from publicity and film scores to elaborate symphonic-style compositions and “Jon and Vangelis”, his duet with Jon Anderson, lead singer of prog rock band Yes.
But he was always wary of commercial success, once telling an interviewer that he never thought of music as mere entertainment.