Sister Teresita Barajuen died overnight Wednesday in her sleep at the Buenafuente del Sistal monastery, northeast of Madrid.
She entered the Cistercian monastery at the age of 19, Sister Maria Romero, the abbess of the monastery said.
Barajuen left the monastery for the first time in 40 years in August 2011 -- to meet the pope in Madrid. She said she kept her eyes closed the whole journey to Madrid to avoid becoming distracted.
Her only other trip away was during the Spanish Civil War to take several of her sisters to see a doctor.
Still, while she lived, Barajuen said she was happy and never bored.
"Even if I had married a prince, I would not be happier than I am now," she once said.