The Portuguese state news agency Lusa confirmed the news on Sunday morning that one of the great figures in world football had passed away.
Nicknamed the 'Black Panther' for his speed and the fear he instilled in his opponents, Mozambique-born Eusebio helped Benfica reach four European Cup finals, winning the tournament in 1962 and being involved in the classic final in 1968 when Benfica lost in extra time to Manchester United.
Eusebio also helped Benfica to 11 Primeira Liga titles between 1961 and 1975, scored 638 goals in 614 matches, and won the Ballon d'Or in 1965.
His international fame peaked during the 1966 England World Cup, when Portugal finished third and Eusebio was top scorer after finding the net nine times during the tournament - with four of those goals coming in the incredible 5-3 quarter-final victory over North Korea at Goodison Park.
His string of stunning performances made him the most famous player in the world at the time as he picked up both the Golden Boot and the Bronze Ball for player of the tournament - as well as the BBC Overseas Sports Personality of the Year award that year.
The death of the charismatic striker, who was idolised throughout the Portuguese-speaking world and considered one of the sport's greatest ever players, was confirmed by state television and the country's sports dailies.
He won 64 caps and scored 41 goals for Portugal, records that stood for almost two decades before being broken.
"He was one of the great figures of Portugal. I think he is immortal. We all know what he meant for football and especially for Portuguese football," Chelsea manager Jose Mourinho told Portugal's state broadcaster RTP.
"He was not only a great inspiration but also an important figure in upholding the values, principles and feelings of football, even after finishing his career," the former Porto, Inter Milan and Real Madrid coach added.
Cristiano Ronaldo also paid tribute to the great man, posting a picture of himself and Eusebio on Twitter.
Eusebio hailed from Lourenco Marques, now Maputo, in colonial Mozambique and as a teenage prodigy was expected to join Benfica's great rivals Sporting Lisbon but changed his mind at the last minute.
Even though he played for Portugal, he was widely regarded as the best known African player of all-time, until the emergence in more recent times of Samuel Eto'o, Didier Drogba and Abedi Pele.
Eusebio ended his career playing in the U.S. but returned to Portugal to various roles with Benfica and the Portuguese federation. He was referred to as the "O Rei" (the king) in his later years, enjoying widespread affection.
Among the first reactions to his death came from former Benfica and Portugal team mate Toni.
"I told him when he was alive much of what I felt... that it was a privilege to have played with him. We have lost one of the greatest figures of Portuguese sport," the former midfielder said in a statement.
"There were many princes in football but few kings. He is in the gallery of the greats. He was gifted both physically and technically, he was like a Greek statue," he added.