Monsignor Georges Marovitch, a former Vatican diplomatic official in Turkey, passed away on Thursday morning.
Msgr. Marovitch was hospitalized on Sunday with a severe blood infection.
His doctor, Hüseyin Fidan, told reporters on Tuesday that Marovitch was in critical condition.
Fidan said the 81-year-old cleric was being supported by a ventilator and that Marovitch's organs were failing due to the blood infection and arrhythmia.
First admitted this weekend, Msgr. Marovitch remained in the intensive care unit at İstanbul's private Sema Hospital until Thursday morning.
Marovitch was a prominent figure in İstanbul and was known for his great efforts to encourage intercultural and interreligious dialogue.
He attended several meetings throughout the 1990s and 2000s to improve relations between different religious communities in Turkey.
He was seriously injured in a 2007 accident in Rome when he was on holiday.
He fell on railroad tracks and was hit by a passing train.
After the incident he was taken to a hospital where he received treatment.