Teoctist invited Pope John Paul to Romania in 1999, the first time a Catholic Pope visited an Orthodox country in a trip aimed at narrowing the age-old split between the two Churches.
"Patriarch Teoctist died at 5:00 pm," Constantin Popa, manager of the Fundeni hospital in Bucharest told reporters.
"He had prostate surgery. Afterwards, he developed heart complications ... which eventually led to his heart failure. He did not respond to resuscitation."
Teoctist, who was born in 1915, had been the head of the Orthodox Church since 1986. Eighty-seven percent of Romanians belong to the Church.
One of his main projects was to build a "Cathedral of the Nation's Absolution", which like the vast Christ the Saviour cathedral in Moscow was to be seen as a symbol of rebirth after 50 years of communist repression. Land and financing problems have delayed its construction, however.
