Samaranch (left) was succeeded by Jacques Rogge
Former International Olympic Committee president Juan Antonio Samaranch has died in hospital after being taken ill at the weekend.
The 89-year-old was admitted to the Quiron Hospital in Barcelona where he was being treated for heart problems.
The Spaniard was widely regarded as the most powerful man in sport when he headed the IOC from 1980 to 2001.
His successor, Jacques Rogge, said: "I cannot find the words to express the distress of the Olympic family."
Rogge continued: "I am personally deeply saddened by the death of the man who built up the Olympic Games of the modern era, a man who inspired me, and whose knowledge of sport was truly exceptional.
He was quite simply the most intuitive leader I have ever met
"Thanks to his extraordinary vision and talent, Samaranch was the architect of a strong and unified Olympic Movement.
"I can only pay tribute to his tremendous achievements and legacy, and praise his genuine devotion to the Olympic Movement and its values.
"We have lost a great man, a mentor and a friend who dedicated his long and fulfilled life to Olympism."
London 2012 chairman Lord Coe, who was close to Samaranch for three decades, said he had been an inspiration.
"I have lost a friend, one that moulded my path through sport from my early 20s, and the world has lost an inspirational man," said Coe.
"A man that challenged us all to fight for sport, its primacy and its autonomy, a fight he led fearlessly from the front, creating an extraordinary sporting movement that reaches millions of people around the world.
"He was quite simply the most intuitive leader I have ever met."
Samaranch, who was admitted to hospital on Sunday with acute heart problems, died from cardio-respiratory failure.
He had been plagued by ill-health in recent years, but continued to travel to IOC meetings around the world, and in February attended the Winter Olympics in Vancouver, walking with the help of a female assistant.
Samaranch retired as IOC president in 2001, after 21 years at the helm. Only Pierre de Coubertin, the "father" of the modern Olympics - and IOC chief from 1896 to 1925 - had held the post for a longer period.
Lamine Diack, president of the International Association of Athletics Federations, said Samaranach had used "the skills of a natural diplomat" to create a unified Olympic movement and make it the "world's most influential sporting event".
"But as well as his unique devotion to the Olympic movement and its values, I will never forget the deep respect and passion that Juan Antonio showed for the sport of athletics," he said.
Dick Pound, a long-standing Canadian IOC member and the first president of the World Anti-Doping Agency, saluted Samaranch for creating an Olympics renaissance.
"He did essentially a two century jump. He got us from being in the remnants of the 19th century and got us into the 21st century," he said.
"He gave the organization financial stability, international presence and a certain gravitas it never had before."
Born in Barcelona on 17 July, 1920, Samaranch enjoyed success as a roller-skater and led the Spanish team to the world title.
He pursued a career in sports politics in fascist dictator Francisco Franco's Spain and won a place on the IOC in 1966.
After Franco's death, Samaranch was appointed ambassador to the Soviet Union and the contacts he made there helped him succeed Lord Killanin as IOC president in 1980. He oversaw the commercialisation of the Olympics during the 1980s and 1990s and established the Games as a world force.
BBC Radio 5 live Olympics correspondent Gordon Farquhar said of Samaranch: "He took over during one of the movement's most difficult times, just before the Moscow games in 1980, which were affected by a US-led boycott in protest at Soviet foreign policy.
"The previous Olympics in Montreal had been a financial disaster, and the games were viewed as a burden, not an opportunity for the host nation. Only Los Angeles bid to stage the 1984 games.
"During his tenure, Samaranch helped revitalise the economic fortunes of the IOC through global sponsorship deals and marketing of TV rights. Professional athletes were fully embraced, finally ending the tradition of amateurism at the games."
During his tenure, Samaranch helped revitalise the economic fortunes of the IOC
BBC Olympics correspondent Gordon Farquhar
Samaranch was criticised in some quarters for not taking the issue of doping seriously enough and for allowing bidding cities to "over-indulge" members.
After 10 IOC members resigned or were expelled following a bribery scandal surrounding the Salt Lake winter Games, he introduced a series of reforms to clean up the organisation, including a ban on member visits to bid cities.
Former British Olympic Association chairman Sir Craig Reedie defended Samaranch over the Salt Lake City scandal, saying: "The good certainly outweighed the bad, if there was any bad at all.
"It was Samaranch who set up the commission to investigate the allegations, it was he who set up the reform commission and it was he who set up the ethics commission.
"Yes he must have been embarrassed by it but he then did something about it."
Simon Clegg, former chief executive of the BOA, said: "He was a masterful politician and his contribution to the development of world sport cannot be underestimated."
Samaranch was made Honorary Life President after standing down in 2001, and in recent years was a key part of Madrid's failed bids to host the Olympics in 2012 and 2016, which were awarded to London and Rio de Janeiro respectively.
Spanish prime minister Jose Luis Rodriguez Zapatero said: "One of Spain's most emblematic figures has left us, a decisive figure in the resurgence of Spanish sport and in the Olympic movement inside our country.
"He was fundamental in Spain being awarded the 1992 Olympics in Barcelona, and those Games were a tremendous success which in great part we owe to him."
French President Nicolas Sarkozy said: "Juan Antonio Samaranch was a very great figure of the Olympic movement. He is the man who furthered the increase in power of the Olympic movement by opening it to all sports and all countries."