Celtic great Tommy Gemmell, who inspired the club to glory in the 1967 European Cup, has died aged 73 after a long illness, the Scottish giants announced on Thursday.
Gemmell scored Celtic's equaliser and played a part in Stevie Chalmers's 84th-minute winner as Celtic came from behind to beat Inter Milan 2-1 in Lisbon in the 1967 final.
It made them Britain's first European champions and saw the team dubbed 'the Lisbon Lions'.
"The whole Celtic Family is mourning his passing and everyone associated with the club sends their thoughts and prayers to his family, his fellow Lions and his many friends at this desperately sad time," Celtic said in a statement.
Gemmell also scored in the 1970 final, when Celtic lost 2-1 to Dutch side Feyenoord in Milan.
He spent 10 years at Celtic Park between 1961 and 1971, making 418 appearances and scoring 63 goals.
In addition to the breakthrough European Cup win, he also amassed six league titles, three Scottish Cups and four Scottish League Cups.
Celtic added: "Tommy Gemmell is a true Celtic legend, part of the greatest side in the club's history and a man who played a pivotal role in our greatest ever triumph when, in Lisbon's Estadio Nacional, 11 men all born within a 30-mile (48.3-kilometre) radius of Celtic Park beat Inter Milan to win the European Cup.
"The legend of the Lisbon Lions was created that night and Tommy and his team-mates were assured their place in the pantheon of Celtic greats.
"And, like the rest of the Lions, Tommy remained humble about his incredible football achievements."
Gemmell joined Nottingham Forest in 1971 and spent two years there.
Following a short spell in the United States with the Miami Toros, he returned to Scotland, joining Dundee and leading them to victory over Celtic in the 1973 League Cup final.
He retired in 1977 and went on to manage Dundee and, over two spells, Albion Rovers.
Former Celtic midfielder and assistant manager Murdo MacLeod told BBC Sport Gemmell was "one of the greats".
The club's former striker John Hartson wrote on Twitter: "Sad news hearing Tommy Gemmell has passed away.. Celtic great thoughts are with his family and close friends, RIP Tommy."
Celtic's arch rivals Rangers said in a statement: "The club would like to send our sincere condolences to the family of Celtic legend Tommy Gemmell.
"He was one of the great Celtic and Scotland players and will be sadly missed. Our thoughts are with Tommy's family and friends at this very difficult time."