European Parliament President David Sassoli has died at the age of 65, his spokesman says.
The Italian former journalist and centre-left politician had been seriously ill for more than two weeks and cancelled all official activities.
Mr Sassoli was admitted to hospital in Italy last month due to a serious complication with his immune system.
He died in the early hours of Tuesday in a hospital in Aviano, his spokesman, Roberto Cuillo, announced on Twitter.
In September, Mr Sassoli was taken to hospital in Strasbourg where he was treated for a severe case of pneumonia caused by legionella.
He later told his followers on social media that he had suffered a relapse while recuperating in Italy.
He worked remotely during October, officially resuming his political duties in November. But he was again hospitalised on 26 December, Italian media report.
“Pneumonia is an ugly beast the important thing is to avoid relapses and the convalescence must be adequate,” he told Italian outlet Corriere in September.
A vote to elect his replacement had already been planned for later this month, and Mr Sassoli had indicated that he would not seek re-election.
The former television newsreader became president of the 705-seat European Parliament in July 2019. He was the second Italian president since the assembly was elected by universal suffrage.
The role is considered one of the bloc’s top jobs, and involves chairing sessions and overseeing the parliament’s activities.
He beat three other candidates to the role, and in a speech following his victory he called for the EU to return to the spirit of its founding fathers who swapped warfare and nationalism for peace and equality.
Mr Sassoli left a three-decade career in journalism and became a member of the European Parliament (MEP) in 2009.
He was a member of the centre-left Progressive Alliance of Socialists and Democrats, the second-biggest grouping in the parliament.
A number of people have paid tribute to Mr Sassoli.
European Council President Charles Michel described Mr Sassoli as a “sincere and passionate European”.
“We already miss his human warmth, his generosity, his friendliness and his smile,” he said.
“What a big shock and a big loss. I am deeply saddened,” MEP Ismail Ertug wrote on Twitter.
Another MEP, Paolo Borchia, expressed condolences to Mr Sassoli’s family and said the news had left him “stunned”.