Former Liverpool manager Gerard Houllier has died at the age of 73.
The Frenchman, who also managed Aston Villa later in his career, guided the Reds to an FA Cup, League Cup and UEFA Cup treble in 2001, the highlight of his six-year spell in charge.
Houllier also managed Paris St Germain, Lyon and the France national team during his career.
"We are mourning the passing of our treble-winning manager, Gerard Houllier," the Premier League champions said on Twitter.
"The thoughts of everyone at Liverpool Football Club are with Gerard's family and many friends. Rest in peace, Gerard Houllier 1947-2020."
The French football federation said it extended "its deepest condolences to the family and friends" of Houllier, who had a long association with the national team as a youth coach, an assistant and head coach between 1992 and 1993.
Houllier left day-to-day management after departing Villa in 2011, and more recently worked as the head of global football for the Red Bull group which owns RB Leipzig, RB Salzburg and the New York Red Bulls, as well as advising Lyon.
Houllier had suffered with heart complications during his career.
In October 2001, he fell ill at half-time during Liverpool's match against Leeds and was diagnosed with an aortic dissection which required emergency surgery and led to a five-month spell out of the dugout.
Houllier suffered further health problems while with Villa.
He was admitted to hospital in April 2011 after falling ill, and would not return to work before stepping down by mutual consent on 1 June.
Former players and peers rook to social media to pay tribute to the Frenchman.
Ex-Liverpool striker Michael Owen tweeted: "Absolutely heartbroken to hear that my old boss, Gerard Houllier, has sadly passed away. A great manager and a genuinely caring man. #RIPBoss."
Absolutely devastated by the news about Gerard Houllier, I was in touch with him only last month to arrange him coming to Liverpool. Loved that man to bits, he changed me as a person & as a player & got @LFC back winning trophies. RIP Boss. ??— Jamie Carragher (@Carra23) December 14, 2020
We are mourning the passing of our treble-winning manager, Gerard Houllier.— Liverpool FC (@LFC) December 14, 2020
The thoughts of everyone at Liverpool Football Club are with Gerard's family and many friends.
Rest in peace, Gerard Houllier 1947-2020. pic.twitter.com/isHGXIfe5E