Note: the following biography is based in large part on the letters and may contain, for that reason, fictionalized elements.

Mariana Alcoforado was born in Beja, daughter of landed proprietor of Alentejo Francisco da Cunha Alcoforado, born at Cortiços, Macedo de Cavaleiros, and first wife Leonor Mendes. She had three brothers, Baltasar Vaz Alcoforado, Miguel da Cunha Alcoforado and Francisco da Cunha Alcoforado and two sisters Ana Maria da Cunha Alcoforado, wife of Rui de Melo Lobo Freire, and Maria Peregrina Alcoforado. Beja was the chief garrison town of the province and the principal theatre of the twenty-eight years' war with Spain that followed the Portuguese Revolution of 1640. Mariana's widowed father, occupied with administrative and military commissions, placed her in the wealthy convent of the Conception for security and education. He later remarried and had two more daughters, Maria da Conceição Alcoforado and Catarina Alcoforado, and was also made a Knight of the Order of Christ on December 15, 1647.

She made her profession as a Franciscan nun of the Poor Ladies at sixteen or earlier, without any real vocation, and lived a routine life in that somewhat relaxed house until her twenty-fifth year, when she purportedly met the young French nobleman Noël Bouton. This man, afterwards known as marquis de Chamilly, and marshal of France, was one of the French officers who came to Portugal to serve under the captain, Frederick Schomberg, 1st Duke of Schomberg, the re-organizer of the Portuguese army, campaigning against the Spanish army in the Alentejo.

During the years 1665-1667 Chamilly spent much of his time in and about Beja, and probably became acquainted with the Alcoforado family through Sóror Mariana's brother, who was a soldier. Custom permitted those in religious orders to receive and entertain visitors, and Chamilly found it easy to get round the trustful nun. Before long their affair became known and caused a scandal, and Chamilly deserted Sóror Mariana and returned to France. This resulted in Sóror Mariana writing the letters.

There are signs in the fifth letter that Sóror Mariana had begun to conquer her passion After a life of rigid penance, accompanied by much suffering, she died, aged 83. Sóror Mariana's life story has also been described in the novel by Katherine Vaz, Mariana, published by Aliform Publishing in 2005.

Fiction

• The Three Marias: New Portuguese Letters, by Maria Isabel Barreno, Maria Teresa Horta, and Maria Velho da Costa, translated by Donald Ericson, 1973 Doubleday; Novas Cartas Portuguesas original title; ISBN 0-385-01853-3.
• The Love Letters, a novel by Madeleine L'Engle, 1966 Farrar, Straus and Giroux, ISBN 0-87788-528-1.

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